fix: Gitea tree loading + auth system overhaul (v2.5.0)

ROOT CAUSE: Local accounts ([email protected]) had no Gitea token linked,
so /api/gitea/.../tree returned 401 → loadGiteaTree() failed silently.

FIXES:
1. _require_gitea() now falls back to admin token for read ops
   → Any logged-in user can browse Gitea repos without linking account
2. get_user_gitea_client() filters by provider='gitea'
   → Prevents using wrong token if user has GitHub+Gitrea linked
3. OAuth callback now stores auth_method correctly
   → gitea_bruno gets auth_method='gitea' instead of 'local'
4. Linked Gitea token to [email protected] (user_id=127)
   → Local account can now use personal token for Gitea API

PREVIOUS FIXES (from prior commit):
- loadGiteaTree: skip if giteaWorkspace already loaded, error logging, .bind(this)
- gitea_workspace.html: use captured 'self' instead of querySelector('[x-data]')
- 12 test assertions updated to reflect admin fallback behavior

app/routers/auth.py

@@ -295,11 +295,11 @@ async def callback(
     login_id = f"{provider_name}_{oauth_user['login']}"
     with get_conn() as conn:
         conn.execute(
-            """INSERT INTO users (login, full_name, email, avatar_url)
-               VALUES (?, ?, ?, ?)
+            """INSERT INTO users (login, full_name, email, avatar_url, auth_method)
+               VALUES (?, ?, ?, ?, ?)
                ON CONFLICT(login)
-               DO UPDATE SET full_name=excluded.full_name, email=excluded.email, avatar_url=excluded.avatar_url""",
-            (login_id, oauth_user.get("full_name", ""), oauth_user.get("email", ""), oauth_user.get("avatar_url", "")),
+               DO UPDATE SET full_name=excluded.full_name, email=excluded.email, avatar_url=excluded.avatar_url, auth_method=excluded.auth_method""",
+            (login_id, oauth_user.get("full_name", ""), oauth_user.get("email", ""), oauth_user.get("avatar_url", ""), provider_name),
         )
         conn.commit()
         # Store OAuth token