feat(i18n): francais comme langue principale, anglais accessible

Le site s'affiche desormais en francais par defaut, avec un selecteur de
langue permettant de basculer vers l'anglais.

Choix de conception : les chaines sources restent en anglais
  Elles servent d'identifiants gettext, et le francais est fourni par
  catalogue avec BABEL_DEFAULT_LOCALE = 'fr'. Le code reste ainsi dans une
  seule langue -- la meme que ses commentaires et docstrings -- tandis que
  ce qu'un membre voit est du francais.

  Consequence qui rend la migration praticable : une chaine non encore
  traduite retombe en anglais, pas sur un identifiant brut. Les gabarits
  peuvent donc etre migres un par un sans jamais laisser le site a moitie
  casse.

Selection de la langue (app/i18n.py)
  1. choix explicite via le selecteur, garde en session
  2. sinon en-tete Accept-Language du navigateur, restreint a fr et en
  3. sinon francais
  Un choix explicite prime toujours, y compris sur un navigateur anglophone.

Selecteur
  Extrait en partiel et inclus dans les deux branches de la mise en page :
  barre laterale une fois connecte, ET page d'authentification. Quelqu'un
  qui ne lit pas la langue courante doit pouvoir en changer AVANT de se
  connecter -- le laisser derriere l'authentification aurait ete un defaut
  d'accessibilite. Chaque langue est ecrite dans sa propre langue.

  La route /lang/<locale> valide le Referer avant de rediriger : sans ce
  controle, elle constituait une redirection ouverte.

Migre dans cette passe
  navigation complete, page de connexion, les cinq pages d'erreur, et
  l'integralite des messages flash de routes/auth.py. 64 chaines, dont
  aucune non traduite.

Verification
  25 tests, dont deux garde-fous d'integrite : un catalogue .mo manquant
  ou une entree non traduite font echouer la suite. Sans cela, une
  compilation oubliee servirait de l'anglais partout, en silence et sans
  rien dans les journaux.

Un test existant a du etre corrige, et c'est instructif
  test_login_failure_message_does_not_reveal_account_existence cherchait la
  sous-chaine anglaise 'attempt(s) remaining'. La page etant desormais en
  francais, elle etait absente des deux cotes, l'assertion passait, et le
  mode strict a signale le faux succes. Le test comparait donc l'anglais,
  pas le comportement. Il compare desormais les messages flash rendus,
  quelle que soit la langue. La faille SEC-AUTH-006 reste ouverte, et le
  test la documente toujours.

Les catalogues .po ET .mo sont versionnes : le deploiement est un simple
miroir de fichiers, sans etape de compilation. messages.pot, regenerable,
ne l'est pas.

docs/translations.md documente le processus, les deux pieges (concatenation
de phrases, traduction a l'import), et l'etat de la migration. A noter pour
la suite : les chaines dans les blocs <script> ne peuvent pas etre balisees
telles quelles, il faudra les passer par des attributs data- -- ce qui
rejoint le chantier de sortie de unsafe-inline (OPS-010).

Co-Authored-By: Claude Opus 5 <[email protected]>

app/translations/en/LC_MESSAGES/messages.po

@@ -0,0 +1,306 @@
+# English translations for team-tryouts.
+# Copyright (C) 2026 UdeS Esports
+# This file is distributed under the same license as the team-tryouts
+# project.
+# FIRST AUTHOR <EMAIL@ADDRESS>, 2026.
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: team-tryouts VERSION\n"
+"Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
+"POT-Creation-Date: 2026-08-07 20:25-0400\n"
+"PO-Revision-Date: 2026-08-07 20:22-0400\n"
+"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
+"Language: en\n"
+"Language-Team: UdeS Esports\n"
+"Plural-Forms: nplurals=2; plural=(n != 1);\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"
+"Generated-By: Babel 2.18.0\n"
+
+#: app/routes/auth.py:141
+#, python-format
+msgid ""
+"Account is locked due to too many failed attempts. Please try again in %(remaining)s "
+"minute(s)."
+msgstr ""
+"Account is locked due to too many failed attempts. Please try again in %(remaining)s "
+"minute(s)."
+
+#: app/routes/auth.py:151
+msgid "This account has been deactivated."
+msgstr "This account has been deactivated."
+
+#: app/routes/auth.py:179
+#, python-format
+msgid "Welcome back, %(username)s!"
+msgstr "Welcome back, %(username)s!"
+
+#: app/routes/auth.py:192
+#, python-format
+msgid ""
+"Account locked after %(attempts)s failed attempts. Please try again in %(minutes)s "
+"minutes."
+msgstr ""
+"Account locked after %(attempts)s failed attempts. Please try again in %(minutes)s "
+"minutes."
+
+#: app/routes/auth.py:201
+#, python-format
+msgid "Login unsuccessful. %(remaining)s attempt(s) remaining before lockout."
+msgstr "Login unsuccessful. %(remaining)s attempt(s) remaining before lockout."
+
+#: app/routes/auth.py:208
+msgid "Login unsuccessful. Please check username and password."
+msgstr "Login unsuccessful. Please check username and password."
+
+#: app/routes/auth.py:239
+msgid "Incorrect CAPTCHA answer. Please try again."
+msgstr "Incorrect CAPTCHA answer. Please try again."
+
+#: app/routes/auth.py:281
+msgid "Username already exists."
+msgstr "Username already exists."
+
+#: app/routes/auth.py:293
+msgid "Email already registered."
+msgstr "Email already registered."
+
+#: app/routes/auth.py:339
+msgid "Your account has been created! You can now log in."
+msgstr "Your account has been created! You can now log in."
+
+#: app/routes/auth.py:365
+msgid "Discord OAuth2 is not configured."
+msgstr "Discord OAuth2 is not configured."
+
+#: app/routes/auth.py:405
+msgid ""
+"Discord authorization could not be verified. Please start the connection again from "
+"this page."
+msgstr ""
+"Discord authorization could not be verified. Please start the connection again from "
+"this page."
+
+#: app/routes/auth.py:413
+msgid "Discord authorization failed. No code received."
+msgstr "Discord authorization failed. No code received."
+
+#: app/routes/auth.py:437
+msgid "Failed to connect to Discord. Please try again."
+msgstr "Failed to connect to Discord. Please try again."
+
+#: app/routes/auth.py:441
+msgid "Failed to obtain Discord access token."
+msgstr "Failed to obtain Discord access token."
+
+#: app/routes/auth.py:456
+msgid "Failed to fetch Discord user profile."
+msgstr "Failed to fetch Discord user profile."
+
+#: app/routes/auth.py:503
+msgid "Discord account connected! Your profile has been pre-filled."
+msgstr "Discord account connected! Your profile has been pre-filled."
+
+#: app/routes/auth.py:521
+msgid "You have been logged out."
+msgstr "You have been logged out."
+
+#: app/templates/errors/400.html:2
+msgid "400 Bad Request"
+msgstr "400 Bad Request"
+
+#: app/templates/errors/400.html:3
+msgid "Bad Request"
+msgstr "Bad Request"
+
+#: app/templates/errors/400.html:9
+msgid "400 — Bad Request"
+msgstr "400 — Bad Request"
+
+#: app/templates/errors/400.html:10
+msgid ""
+"The request could not be understood by the server. Please check your input and try "
+"again."
+msgstr ""
+"The request could not be understood by the server. Please check your input and try "
+"again."
+
+#: app/templates/errors/400.html:12 app/templates/errors/403.html:12
+#: app/templates/errors/429.html:12
+msgid "Go Back"
+msgstr "Go Back"
+
+#: app/templates/errors/403.html:2
+msgid "403 Forbidden"
+msgstr "403 Forbidden"
+
+#: app/templates/errors/403.html:3
+msgid "Access Denied"
+msgstr "Access Denied"
+
+#: app/templates/errors/403.html:9
+msgid "403 — Forbidden"
+msgstr "403 — Forbidden"
+
+#: app/templates/errors/403.html:10
+msgid ""
+"You do not have permission to access this resource. If you believe this is an error, "
+"please contact an administrator."
+msgstr ""
+"You do not have permission to access this resource. If you believe this is an error, "
+"please contact an administrator."
+
+#: app/templates/errors/404.html:2
+msgid "404 Not Found"
+msgstr "404 Not Found"
+
+#: app/templates/errors/404.html:3
+msgid "Page Not Found"
+msgstr "Page Not Found"
+
+#: app/templates/errors/404.html:9
+msgid "404 — Not Found"
+msgstr "404 — Not Found"
+
+#: app/templates/errors/404.html:10
+msgid "The page you are looking for does not exist. It may have been moved or deleted."
+msgstr "The page you are looking for does not exist. It may have been moved or deleted."
+
+#: app/templates/errors/404.html:12
+msgid "Return Home"
+msgstr "Return Home"
+
+#: app/templates/errors/429.html:2
+msgid "429 Too Many Requests"
+msgstr "429 Too Many Requests"
+
+#: app/templates/errors/429.html:3
+msgid "Rate Limit Exceeded"
+msgstr "Rate Limit Exceeded"
+
+#: app/templates/errors/429.html:9
+msgid "429 — Too Many Requests"
+msgstr "429 — Too Many Requests"
+
+#: app/templates/errors/429.html:10
+msgid "You have sent too many requests in a short period. Please wait a moment and try again."
+msgstr "You have sent too many requests in a short period. Please wait a moment and try again."
+
+#: app/templates/errors/500.html:2
+msgid "500 Server Error"
+msgstr "500 Server Error"
+
+#: app/templates/errors/500.html:3
+msgid "Internal Server Error"
+msgstr "Internal Server Error"
+
+#: app/templates/errors/500.html:9
+msgid "500 — Internal Server Error"
+msgstr "500 — Internal Server Error"
+
+#: app/templates/errors/500.html:10
+msgid ""
+"Something went wrong on our end. The error has been logged and will be investigated. "
+"Please try again later."
+msgstr ""
+"Something went wrong on our end. The error has been logged and will be investigated. "
+"Please try again later."
+
+#: app/templates/errors/500.html:12
+msgid "Try Again"
+msgstr "Try Again"
+
+#: app/templates/layouts/_language_switcher.html:10
+msgid "Language"
+msgstr "Language"
+
+#: app/templates/layouts/base.html:33 app/templates/layouts/base.html:133
+msgid "Dashboard"
+msgstr "Dashboard"
+
+#: app/templates/layouts/base.html:39
+msgid "Tryouts"
+msgstr "Tryouts"
+
+#: app/templates/layouts/base.html:45
+msgid "Calendar"
+msgstr "Calendar"
+
+#: app/templates/layouts/base.html:52
+msgid "Evaluations"
+msgstr "Evaluations"
+
+#: app/templates/layouts/base.html:60
+msgid "My Team(s)"
+msgstr "My Team(s)"
+
+#: app/templates/layouts/base.html:67
+msgid "Manage Teams"
+msgstr "Manage Teams"
+
+#: app/templates/layouts/base.html:75
+msgid "Manage Users"
+msgstr "Manage Users"
+
+#: app/templates/layouts/base.html:83
+msgid "My Notes"
+msgstr "My Notes"
+
+#: app/templates/layouts/base.html:91
+msgid "Availability"
+msgstr "Availability"
+
+#: app/templates/layouts/base.html:97
+msgid "Notes & One on One"
+msgstr "Notes & One on One"
+
+#: app/templates/layouts/base.html:104
+msgid "Contracts"
+msgstr "Contracts"
+
+#: app/templates/layouts/base.html:111
+msgid "My Profile"
+msgstr "My Profile"
+
+#: app/templates/layouts/base.html:117
+msgid "Logout"
+msgstr "Logout"
+
+#: app/templates/layouts/base.html:175
+msgid "Team Tryout Management System"
+msgstr "Team Tryout Management System"
+
+#: app/templates/pages/login.html:2
+msgid "Login"
+msgstr "Login"
+
+#: app/templates/pages/login.html:7
+msgid "Username"
+msgstr "Username"
+
+#: app/templates/pages/login.html:8
+msgid "Enter your username"
+msgstr "Enter your username"
+
+#: app/templates/pages/login.html:11
+msgid "Password"
+msgstr "Password"
+
+#: app/templates/pages/login.html:12
+msgid "Enter your password"
+msgstr "Enter your password"
+
+#: app/templates/pages/login.html:14
+msgid "Sign In"
+msgstr "Sign In"
+
+#: app/templates/pages/login.html:15
+msgid "Don't have an account?"
+msgstr "Don't have an account?"
+
+#: app/templates/pages/login.html:15
+msgid "Register here"
+msgstr "Register here"
+