perf: switch Qdrant to AsyncQdrantClient with explicit timeout

Every vector call ran on the sync QdrantClient inside async wrapper
methods, blocking the FastAPI event loop per Qdrant round-trip. The
wrapper now holds an AsyncQdrantClient (timeout via QDRANT_TIMEOUT,
default 30s) and awaits all client calls; the wrapper API is unchanged.

Call sites off the wrapper were fixed too: the HybridRAG document leg
now uses the async search_vectors wrapper instead of the deprecated raw
client.search (also fixing its call to the nonexistent ollama.embed_text
which made the leg permanently report 'failed'), the health check awaits
get_collections, and document_sync's raw delete/upsert calls are awaited
(routed through wrappers in the next commit).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QbFZyDvYksazX6nYQYZ67L

src/services/document_sync_service.py

@@ -198,7 +198,7 @@ class DocumentSyncService:
 
         # Delete existing chunks for this document
         try:
-            self.qdrant.client.delete(
+            await self.qdrant.client.delete(
                 collection_name=collection,
                 points_selector={
                     "filter": {
@@ -242,7 +242,7 @@ class DocumentSyncService:
 
         # Upsert to Qdrant
         if points:
-            self.qdrant.client.upsert(
+            await self.qdrant.client.upsert(
                 collection_name=collection,
                 points=points
             )