ci: harden the qdrant integration job

The integration test job has been failing intermittently on main and on
open pull requests with `httpx.ReadTimeout: timed out` on the first write
to Qdrant, while `GET /collections` and `/healthz` kept answering.

Cause: the qdrant-client default request timeout is 5 seconds, and the job
only waits for `/healthz`, which is served before the storage engine
accepts writes. On a shared runner doing several builds at once, the first
collection creation or indexing exceeds 5s and the whole fixture errors
out.

- pin qdrant/qdrant to v1.19 (the digest `latest` and the cluster already
  run) and let Renovate track the pin in the workflows as well
- wait for a real write round-trip (create + delete a probe collection)
  instead of `/healthz` alone, and dump the container logs if it never
  becomes writable
- make the Qdrant client timeout configurable via QDRANT_TIMEOUT and set
  it to 60s in CI, where there is no latency SLA

src/server.py

@@ -36,6 +36,10 @@ COLLECTION_NAME = os.environ.get("COLLECTION_NAME", "")
 EMBEDDING_MODEL_NAME = os.environ.get("EMBEDDING_MODEL_NAME", "BAAI/bge-small-en-v1.5")
 DEFAULT_LIMIT = int(os.environ.get("SEARCH_LIMIT", "50"))
 
+# Per-request timeout (seconds) for Qdrant. The client default is 5s, which is
+# tight for a cold collection or a busy host: unset means keep that default.
+QDRANT_TIMEOUT = int(os.environ["QDRANT_TIMEOUT"]) if os.environ.get("QDRANT_TIMEOUT") else None
+
 if not QDRANT_URL:
     raise ValueError("QDRANT_URL environment variable is required.")
 if not COLLECTION_NAME:
@@ -60,8 +64,8 @@ def get_qdrant_client() -> QdrantClient:
     """Returns a singleton Qdrant client."""
     global _qdrant_client
     if _qdrant_client is None:
-        logger.info(f"Connecting to Qdrant at {QDRANT_URL}")
-        _qdrant_client = QdrantClient(url=QDRANT_URL)
+        logger.info(f"Connecting to Qdrant at {QDRANT_URL} (timeout={QDRANT_TIMEOUT})")
+        _qdrant_client = QdrantClient(url=QDRANT_URL, timeout=QDRANT_TIMEOUT)
     return _qdrant_client