fix(vector-sync): use resolved collection name in orphan sweep

The startup sweep was reading settings.qdrant_collection (the raw config
value, default "nextcloud_content") instead of settings.get_collection_name(),
which is what every other vector-sync operation uses. When QDRANT_COLLECTION
is not overridden, get_collection_name() auto-generates a
{deployment-id}-{model-name} name; the sweep was targeting a non-existent
collection and silently returning (0, 0).

Also adds the AsyncQdrantClient type annotation that was missing on
sweep_orphan_placeholders, and renames its parameter from collection_name
to collection to make it clear the value must be the resolved name.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

nextcloud_mcp_server/app.py

@@ -1452,15 +1452,14 @@ def get_app(transport: str = "streamable-http", enabled_apps: list[str] | None =
             return
         try:
             qdrant_client = await get_qdrant_client()
-            swept, kept = await sweep_orphan_placeholders(
-                qdrant_client, settings.qdrant_collection
-            )
+            collection = settings.get_collection_name()
+            swept, kept = await sweep_orphan_placeholders(qdrant_client, collection)
             logger.info(
                 "vector_sync.orphan_sweep",
                 extra={
                     "swept": swept,
                     "kept": kept,
-                    "collection": settings.qdrant_collection,
+                    "collection": collection,
                 },
             )
         except Exception: