Ruff-Cleanup: ganzes MC2-Repo lint-grün + projekt-passende ruff.toml

Die Ampel-Nachruestung deckte 317/337 vorbestehende ruff-Verstoesse im ganzen Repo
auf. Aufgeraeumt:
- ruff.toml: intentionale Muster als Projekt-Politik ausgenommen (BLE001 blind-except,
  S110/S112 try-except-pass/continue, PLW1510 subprocess-best-effort, B008 FastAPI-
  Depends/File-Idiom, EXE001 Shebang, + wenige Stil-Regeln). __init__.py-Re-Exports
  geschuetzt (F401).
- ruff --fix: 128 mechanische (Import-Sortierung, PEP585/604-Annotationen, tote Imports,
  ueberfluessige noqa) auto-behoben.
- 12 echte Reste von Hand: PERF402/102, PLC3002 (Lambda->walrus), ISC004 (String-Concat
  geklammert), F841/RUF059 (ungenutzte Vars), PIE810 (startswith-Tuple), UP031 (f-string),
  UP035 (veraltete typing-Imports).
Ergebnis: 'ruff check .' = 0, 'compileall' grün. Kein Verhaltenswechsel (nur Stil/Modernisierung).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/routers/system.py

@@ -9,12 +9,10 @@ import logging
 import os
 import subprocess
 
+import httpx
+from config import GATEWAY_URL, HERMES_API_URL, LLAMA_SWAP_URL, MEM0_SERVICE_URL, V1_UPSTREAM, VOICE_SERVICE_URL
 from fastapi import APIRouter
 from pydantic import BaseModel
-
-import httpx
-
-from config import GATEWAY_URL, HERMES_API_URL, LLAMA_SWAP_URL, MEM0_SERVICE_URL, V1_UPSTREAM, VOICE_SERVICE_URL
 from services import backup as backup_svc
 from services import maintenance
 from services.agent import agent_status
@@ -67,7 +65,7 @@ def _user_unit_active(unit: str) -> bool:
         r = subprocess.run(["systemctl", "--user", "is-active", unit],
                            capture_output=True, text=True, timeout=3)
         return r.stdout.strip() == "active"
-    except Exception:  # noqa: BLE001
+    except Exception:
         return False
 
 
@@ -135,7 +133,7 @@ def _run(cmd: list[str], cwd: str | None = None) -> dict:
         p = subprocess.run(cmd, cwd=cwd, capture_output=True, text=True, timeout=180)
         return {"ok": p.returncode == 0, "code": p.returncode,
                 "out": (p.stdout or "")[-2000:], "err": (p.stderr or "")[-2000:]}
-    except Exception as exc:  # noqa: BLE001
+    except Exception as exc:
         return {"ok": False, "code": -1, "out": "", "err": str(exc)}