fix: protect dashboard / route with auth check

Dashboard now calls _get_user_or_redirect() before rendering.
Unauthenticated users get redirected to /auth/login?provider=local.
All sensitive routes now protected: /, /workspace, /accounts/settings

app/routers/dashboard.py

@@ -292,6 +292,9 @@ async def dashboard(
     search: str = Query(default=""),
     show_archived: bool = Query(default=False),
 ):
+    auth = _get_user_or_redirect(request)
+    if isinstance(auth, RedirectResponse):
+        return auth
     try:
         repos = await gitea.get_user_repos(page=1, limit=50)
         if search: