feat(v5.2.0): finalize Infrastructure & Polish (tests isolation, xdist, lint, CI)

tests/conftest.py: mutate the settings singleton (instead of rebinding) so DB + backup dir are isolated per test -> pytest-xdist safe.
Real backup tests (snapshot/prune/admin API) and OAuth mock tests (Gitea/GitHub/link) replace the previous skips.
init_db() now also creates webhook_subscriptions (full schema without the FastAPI lifespan).
ruff check is clean; .eslintrc.json migrated to eslint.config.mjs (flat config).
CI: lint job (ruff + eslint), parallel tests (-n auto), run on every branch push.
VERSION 5.11.1.

app/routers/gitea.py

@@ -7,7 +7,7 @@ router = APIRouter(tags=["gitea"], prefix="/api/gitea")
 
 def _require_gitea(request: Request):
     """Return a per-user GiteaClient or raise 401.
-    
+
     Only returns a client if the user has personally connected their Gitea
     account (OAuth token). No fallback to admin token — each user must link
     their own Gitea account to see Gitea projects.
@@ -160,8 +160,8 @@ async def get_labels(request: Request, owner: str, repo: str):
     try:
         labels = await gitea.get_labels(owner, repo)
         return {"labels": [
-            {"id": l["id"], "name": l["name"], "color": l.get("color", "#787774")}
-            for l in labels
+            {"id": lbl["id"], "name": lbl["name"], "color": lbl.get("color", "#787774")}
+            for lbl in labels
         ]}
     except Exception as e:
         return JSONResponse({"error": str(e)}, status_code=502)
@@ -327,7 +327,8 @@ async def sync_labels(request: Request, owner: str, repo: str):
         for label in labels:
             name = label.get("name", "")
             color = label.get("color", "#787774")
-            if not name: continue
+            if not name:
+                continue
             existing = conn.execute(
                 "SELECT id FROM tags WHERE name=? AND user_id=?", (name, user["id"])
             ).fetchone()