fix: separate Authentik application slug from OAuth client ID

Authentik uses different values for:
- OAuth Client ID (UUID for authentication)
- Application Slug (URL-friendly identifier like 'headquarter-web')

Add AUTHENTIK_APPLICATION_SLUG config to build correct Authentik URLs
while keeping AUTHENTIK_CLIENT_ID for OAuth token exchange.

apps/api/src/config.py

@@ -34,6 +34,9 @@ class Settings(BaseSettings):
     # Authentik configuration - no hardcoded URLs
     authentik_client_id: str = "headquarter-web"
     authentik_client_secret: str = "change-me"
+    # Authentik application slug used in URLs (e.g., "headquarter-web")
+    # This is different from the OAuth client_id which may be a UUID
+    authentik_application_slug: str = "headquarter-web"
     authentik_authorize_url: str | None = None
     authentik_token_url: str | None = None
     authentik_jwks_url: str | None = None
@@ -100,13 +103,13 @@ class Settings(BaseSettings):
     def resolved_authentik_jwks_url(self) -> str:
         if self.authentik_jwks_url:
             return self.authentik_jwks_url
-        return f"{self.authentik_base_url}/application/o/{self.authentik_client_id}/jwks/"
+        return f"{self.authentik_base_url}/application/o/{self.authentik_application_slug}/jwks/"
 
     @property
     def resolved_authentik_issuer(self) -> str:
         if self.authentik_issuer:
             return self.authentik_issuer
-        return f"{self.authentik_base_url}/application/o/{self.authentik_client_id}/"
+        return f"{self.authentik_base_url}/application/o/{self.authentik_application_slug}/"
 
     @property
     def cookie_secure(self) -> bool: