feat(mobile): identité user-first — login/password, SecureStore, scoping par compte

- api: DeviceRegistration device-only, login/changePassword/resolveUser, interception 401 (purge) exonérée sur le login ; type User aligné sur le fil (is_admin)
- SecureStore (expo-secure-store v57) : token + profil, jamais en SQLite ; miroir active_user_id
- AuthContext : statut loading/signedOut/signedIn, bootstrap register→restore, signIn/signOut, garde-fou switch de compte
- app/login.tsx + gate de routes dans _layout (Redirect signedOut) ; i18n fr/en
- DB v5 : user_id sur pending_operations + resource_permissions (UNIQUE par user), repos scopés (user_id IS ? OR IS NULL)
- syncOutbox : delta permissions par compte (Map), outbox poussée du compte actif uniquement
- tests: register/login/401/resolve/changePassword, scoping outbox+permissions, migrations v5 ; e2e live revert register→login admin

mobile/i18n/en.json

@@ -8,5 +8,17 @@
   "empty_folder": "Empty folder — next syncDevice will refresh it.",
   "bytes": "B",
   "kilobytes": "KB",
-  "megabytes": "MB"
+  "megabytes": "MB",
+  "login_title": "Sign in",
+  "login_subtitle": "Sign in to your account",
+  "login_username": "Username",
+  "login_password": "Password",
+  "login_submit": "Sign in",
+  "login_submitting": "Signing in…",
+  "login_error_required": "Username and password are required",
+  "login_error_generic": "Could not sign in right now",
+  "login_switch_title": "Account already signed in",
+  "login_switch_message": "This sign-in will replace the active account on this device. Continue?",
+  "login_switch_confirm": "Replace",
+  "login_switch_cancel": "Cancel"
 }

mobile/i18n/fr.json

@@ -8,5 +8,17 @@
   "empty_folder": "Dossier vide — le prochain syncDevice l'actualisera.",
   "bytes": "o",
   "kilobytes": "Ko",
-  "megabytes": "Mo"
+  "megabytes": "Mo",
+  "login_title": "Connexion",
+  "login_subtitle": "Connecte-toi à ton compte",
+  "login_username": "Nom d'utilisateur",
+  "login_password": "Mot de passe",
+  "login_submit": "Se connecter",
+  "login_submitting": "Connexion…",
+  "login_error_required": "Nom d'utilisateur et mot de passe requis",
+  "login_error_generic": "Impossible de se connecter pour le moment",
+  "login_switch_title": "Compte déjà connecté",
+  "login_switch_message": "Cette connexion remplacera le compte actif sur cet appareil. Continuer ?",
+  "login_switch_confirm": "Remplacer",
+  "login_switch_cancel": "Annuler"
 }