feat: redirect_uri dynamique basé sur Host header

Avant: oauth_redirect_uri codé en dur à localhost:8080
→ impossible d'utiliser l'OAuth depuis une autre machine du réseau

Après: le redirect_uri est construit à partir du header Host de la requête
→ localhost:8080 → http://localhost:8080/auth/callback
→ 192.168.30.101:8080 → http://192.168.30.101:8080/auth/callback

⚠️ L'utilisateur doit ajouter les 2 URIs dans Gitea OAuth App settings.

app/auth/providers.py

@@ -22,11 +22,11 @@ class OAuthProvider(ABC):
         """Whether this provider is configured."""
 
     @abstractmethod
-    def get_authorize_url(self, state: str) -> str:
+    def get_authorize_url(self, state: str, redirect_uri: str | None = None) -> str:
         """Build the authorization URL."""
 
     @abstractmethod
-    async def exchange_code(self, code: str) -> dict | None:
+    async def exchange_code(self, code: str, redirect_uri: str | None = None) -> dict | None:
         """Exchange authorization code for access token."""
 
     @abstractmethod
@@ -53,25 +53,25 @@ class GiteaProvider(OAuthProvider):
     def is_enabled(self) -> bool:
         return bool(self.client_id and self.client_secret)
 
-    def get_authorize_url(self, state: str) -> str:
+    def get_authorize_url(self, state: str, redirect_uri: str | None = None) -> str:
         return (
             f"{self.base}/login/oauth/authorize?"
             + urlencode({
                 "client_id": self.client_id,
-                "redirect_uri": self.redirect_uri,
+                "redirect_uri": redirect_uri or self.redirect_uri,
                 "response_type": "code",
                 "state": state,
             })
         )
 
-    async def exchange_code(self, code: str) -> dict | None:
+    async def exchange_code(self, code: str, redirect_uri: str | None = None) -> dict | None:
         url = f"{self.base}/login/oauth/access_token"
         data = {
             "client_id": self.client_id,
             "client_secret": self.client_secret,
             "code": code,
             "grant_type": "authorization_code",
-            "redirect_uri": self.redirect_uri,
+            "redirect_uri": redirect_uri or self.redirect_uri,
         }
         async with httpx.AsyncClient(timeout=15) as client:
             r = await client.post(url, json=data, headers={"Accept": "application/json"})
@@ -143,18 +143,18 @@ class GitHubProvider(OAuthProvider):
     def is_enabled(self) -> bool:
         return bool(self.client_id and self.client_secret)
 
-    def get_authorize_url(self, state: str) -> str:
+    def get_authorize_url(self, state: str, redirect_uri: str | None = None) -> str:
         return (
             f"{self.authorize_url}?"
             + urlencode({
                 "client_id": self.client_id,
-                "redirect_uri": self.redirect_uri,
+                "redirect_uri": redirect_uri or self.redirect_uri,
                 "scope": "repo,user",
                 "state": state,
             })
         )
 
-    async def exchange_code(self, code: str) -> dict | None:
+    async def exchange_code(self, code: str, redirect_uri: str | None = None) -> dict | None:
         async with httpx.AsyncClient(timeout=15) as client:
             r = await client.post(
                 self.token_url,