fix: github_routes use access_token (not github_token)

user_oauth_tokens has generic access_token column, not github_token/gitea_token

app/routers/github_routes.py

@@ -15,7 +15,7 @@ async def github_status(request: Request):
         return {"linked": False}
     with get_conn() as conn:
         row = conn.execute(
-            "SELECT github_token FROM user_oauth_tokens WHERE user_id=? AND provider='github' AND github_token IS NOT NULL AND github_token != ''",
+            "SELECT access_token FROM user_oauth_tokens WHERE user_id=? AND provider='github' AND access_token IS NOT NULL AND access_token != ''",
             (user["id"],)
         ).fetchone()
     return {"linked": row is not None}