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.

src/cli/qdrant_bootstrap.py

@@ -0,0 +1,54 @@
+"""Create the `chunks` collection — the Qdrant analogue of `alembic upgrade head`.
+
+    uv run python -m src.cli.qdrant_bootstrap
+
+A deployment step, deliberately not part of the FastAPI lifespan: collection
+creation is DDL, which ADR-0009 keeps out of application startup for Postgres
+and ADR-0012 keeps out of it for LangGraph's `.setup()`. See
+`src/infrastructure/qdrant/collection.py` for the full reasoning.
+
+Idempotent and safe to re-run. Exits non-zero if an existing collection
+diverges from the pinned schema, rather than leaving a silently degraded
+sparse index behind.
+"""
+
+import asyncio
+import sys
+
+import structlog
+
+from src.config import Settings
+from src.infrastructure.observability.logging import configure_logging
+from src.infrastructure.qdrant.client import create_client
+from src.infrastructure.qdrant.collection import (
+    CollectionSchemaMismatchError,
+    ensure_chunks_collection,
+)
+
+logger = structlog.get_logger(__name__)
+
+
+async def bootstrap(settings: Settings | None = None) -> int:
+    resolved = settings or Settings()
+    configure_logging(resolved.logging)
+    client = create_client(resolved.qdrant)
+    try:
+        created = await ensure_chunks_collection(client, collection=resolved.qdrant.collection)
+    except CollectionSchemaMismatchError as exc:
+        logger.error("qdrant.bootstrap.schema_mismatch", error=str(exc))
+        return 1
+    finally:
+        await client.close()
+
+    logger.info(
+        "qdrant.bootstrap.completed", collection=resolved.qdrant.collection, created=created
+    )
+    return 0
+
+
+def main() -> None:
+    sys.exit(asyncio.run(bootstrap()))
+
+
+if __name__ == "__main__":
+    main()