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/config.py

@@ -40,6 +40,7 @@ class Settings(BaseSettings):
     # Qdrant Configuration
     qdrant_host: str = Field(default="qdrant", description="Qdrant host")
     qdrant_port: int = Field(default=6333, description="Qdrant port")
+    qdrant_timeout: int = Field(default=30, ge=1, le=300, description="Qdrant client timeout in seconds")
 
     # Wiki.js Configuration
     wikijs_url: str = Field(default="http://wiki:3000", description="Wiki.js URL")