fix: Mi2-Mi4 + Mi1 partial — version pins, file-lock, catalog lock, __main__ tests

- Mi2: requirements.txt — Obergrenzen hinzugefügt (<3.0, <5.0, etc.)
- Mi3: cmd_scan() — File-Lock via fcntl (data_dir/.scan.lock)
- Mi4: refresh_catalog() — Cache-Check unter self._lock (thread-safe)
- Mi1: tests/test_main.py — 17 neue Tests (__main__ Coverage 10% → 18%)
- 294/294 Tests grün

scanner/ai_analyzer.py

@@ -163,14 +163,16 @@ class ModelRouter:
 
     def refresh_catalog(self) -> None:
         """OpenRouter /models + lokale Server /models ziehen (24 h gecacht).
-        Failsafe: blockiert nie."""
+        Failsafe: blockiert nie. Thread-safe via self._lock."""
         if not self._refresh:
             return
-        fetched_at = self._catalog.get("fetched_at")
-        slugs = self._catalog.get("slugs") or []
-        servers = self._catalog.get("servers") or {}
-        if fetched_at and (slugs or servers) and (time.time() - fetched_at) < 86400:
-            return  # Cache frisch
+        # Cache-Check unter Lock — vermeidet doppelte Fetches bei parallelen Scans
+        with self._lock:
+            fetched_at = self._catalog.get("fetched_at")
+            slugs = self._catalog.get("slugs") or []
+            servers = self._catalog.get("servers") or {}
+            if fetched_at and (slugs or servers) and (time.time() - fetched_at) < 86400:
+                return  # Cache frisch
 
         new_slugs, new_servers = [], {}
         # 1. OpenRouter-Katalog (primär)