feat(qdrant): provision the chunks collection as an explicit deployment step

Why:
- The chunks collection needs four named vectors (dense_nomic, dense_openai,
  sparse, late_interaction) and payload indexes defined at creation time per
  ADR-0001; sparse/multivector fields cannot be added to an existing
  collection without recreating it, so schema drift here is expensive.
- Creating it at FastAPI startup would mirror the DDL-at-boot anti-pattern
  ADR-0009 already rejects for Postgres and ADR-0012 rejects for LangGraph's
  setup(), so it is a deployment step instead.

Changes:
- src/infrastructure/qdrant/collection.py: ensure_chunks_collection(),
  idempotent and schema-verifying (raises on dimension/modifier mismatch
  rather than silently accepting a misconfigured collection).
- src/cli/qdrant_bootstrap.py: the operator entry point
  (python -m src.cli.qdrant_bootstrap).
- QdrantSettings gains collection/upsert_batch_size/upsert_concurrency.

Impact:
- Deployments must run the new bootstrap command before the first upload;
  see ADR-0001's new "Collection provisioning" section.

tests/integration/qdrant/conftest.py

@@ -0,0 +1,52 @@
+import uuid
+from collections.abc import AsyncIterator, Iterator
+
+import pytest
+import pytest_asyncio
+from qdrant_client import AsyncQdrantClient
+from testcontainers.community.qdrant import QdrantContainer
+
+from src.config import QdrantSettings
+from src.infrastructure.qdrant.client import create_client
+
+# Pinned to match the `qdrant-client` major/minor in pyproject.toml. The
+# testcontainers default image trails it far enough that the client emits an
+# incompatibility warning, and testing against a version we do not deploy is
+# the wrong signal anyway.
+_QDRANT_IMAGE = "qdrant/qdrant:v1.19.0"
+
+
+@pytest.fixture(scope="session")
+def qdrant_container() -> Iterator[QdrantContainer]:
+    with QdrantContainer(image=_QDRANT_IMAGE) as container:
+        yield container
+
+
+@pytest.fixture(scope="session")
+def qdrant_url(qdrant_container: QdrantContainer) -> str:
+    """The container's REST URL, pinned to IPv4.
+
+    Same gotcha as postgres_url/minio_settings (see their conftests):
+    testcontainers reports the host as `localhost`, which resolves to `::1`
+    first, but Docker publishes the mapped port on IPv4 only. The IPv6 SYN is
+    dropped rather than refused, so the client hangs until its timeout instead
+    of falling back to the second address -- the connection does not fail, it
+    hangs.
+    """
+    host = qdrant_container.get_container_host_ip().replace("localhost", "127.0.0.1")
+    return f"http://{host}:{qdrant_container.get_exposed_port(6333)}"
+
+
+@pytest.fixture
+def qdrant_settings(qdrant_url: str) -> QdrantSettings:
+    """Settings naming a collection unique to this test (ADR-0016 isolation)."""
+    return QdrantSettings(url=qdrant_url, collection=f"chunks_{uuid.uuid4().hex}")
+
+
+@pytest_asyncio.fixture(loop_scope="session")
+async def qdrant_client(qdrant_settings: QdrantSettings) -> AsyncIterator[AsyncQdrantClient]:
+    client = create_client(qdrant_settings)
+    try:
+        yield client
+    finally:
+        await client.close()