fix: ruff linter warnings

backend/routers/wissen.py

@@ -135,7 +135,7 @@ def graph_vault() -> dict:
             target = VAULT / n["id"]
             content = target.read_text(encoding="utf-8", errors="replace")
             # Set, um mehrfache Links auf dieselbe Datei zu entduplizieren
-            found_links = set(m.group(1).strip().lower() for m in link_rx.finditer(content))
+            found_links = {m.group(1).strip().lower() for m in link_rx.finditer(content)}
             
             for link in found_links:
                 target_id = name_to_id.get(link)

backend/services/auftragsbuch.py

@@ -77,7 +77,7 @@ def _fetch_ci_status(repo: str, branch: str, head_sha: str) -> str | None:
     # Nur auf der Box (wo creds liegen) sinnvoll
     creds = _gitea_creds()
     if not creds: return None
-    user, token = creds
+    _user, token = creds
     cache_key = (repo, branch, head_sha)
     cached = _CI_CACHE.get(cache_key)
     if cached and (time.time() - cached["ts"] < 30 or cached["status"] in ("success", "failure", "skipped")):