feat: add init sidecar for migrations and setup on compose up

Introduces a one-shot `init` service in docker-compose that runs Postgres
migrations, Neo4j index setup, and library-type seeding on every `up`.
Long-running services (`app`, `mcp`, `worker`) now depend on its
successful completion via `service_completed_successfully`, blocking the
stack on configuration errors (missing embedding model, dimension
mismatch, unreachable DB) rather than serving silent zero-result
searches.

Also standardizes reranker test fixtures to use the `/v1` OpenAI-style
base URL convention used across other service clients.

docker/entrypoint.sh

@@ -55,6 +55,19 @@ case "$1" in
     python manage.py load_library_types
     ;;
 
+  init)
+    # Bundled one-shot init run by the `init` sidecar on every
+    # `docker compose up`. Idempotent: re-runs are no-ops unless migrations
+    # or indexes need to change. A non-zero exit here blocks `app`, `mcp`,
+    # and `worker` from starting, which is the point — we'd rather fail
+    # loudly than serve silent zero-result searches.
+    set -e
+    python manage.py migrate --noinput
+    python manage.py setup_neo4j_indexes
+    python manage.py load_library_types
+    ;;
+
+
   shell)
     # Drop into the management shell for ad-hoc work.
     exec python manage.py shell