Add local Docker vector databases and prefilled adapter settings

[CompleteDotTech]

Summary

Adds a complete local Docker path for the open-source vector databases supported by the Vector DB setup UI:

• Qdrant
• PostgreSQL with pgvector
• Weaviate
• Milvus (standalone with etcd and MinIO)

The change also makes the existing adapter forms usable for the local deployment by pre-filling the connection values returned by each adapter schema.

Implementation

• Adds persistent Compose services, volumes, health checks, and a pgvector initialization script.
• Uses internal Compose DNS names for backend/worker connections.
• Adds local HTTP handling to the Weaviate adapter while preserving the existing Weaviate Cloud path.
• Pins the compatible weaviate-client version and updates the affected lockfiles.
• Adds schema regression coverage for the local defaults.
• Documents service ports, volumes, credentials, and local-vs-external connection settings.
• Pinecone remains cloud-managed and is not presented as a local container.

The local Postgres schema defaults are development defaults from the Train Compose environment. Deployments with different essentials.env values should replace those fields before submitting the adapter.

Live Train deployment

Deployed at https://etl.home.complete.tech:

• Onboarding route: https://etl.home.complete.tech/mock_org/onboard (HTTP 200).
• All 13 application containers are running with zero restarts.
• Qdrant, pgvector/Postgres, Weaviate, and the Milvus/etcd/MinIO stack are running in six separate containers.
• The backend exposes local defaults for all four adapters, including the Postgres form fields that were previously blank.
• Worker-side connection tests passed for all four adapters; each test created, queried, and removed a temporary collection/table.
• The public health endpoint correctly returns HTTP 401 without authentication; no credentialed extraction workflow is claimed here.

The deployed application images were built from an isolated merge of the latest Train checkout with this PR, so concurrent uncommitted host files and persistent vector volumes were preserved.

Validation

• SDK schema and Weaviate adapter tests: 4 passed.
• JSON, whitespace, Python, shell, Compose, and lockfile validation completed.
• Live backend schema defaults verified.
• Live worker adapter tests passed for Qdrant, Postgres/pgvector, Weaviate, and Milvus.