fix: load the app-local .env in full during local startup

[LanT33]

Summary

• Fix silent truncation of the app-local .env during local startup.
• Explicitly add --env-file for uv loads.
• Impact: none — local-dev configuration and documentation only.
• link the related issue [Bug]: The local .env file is not loaded, so the api and worker start with code defaults #440

Verification

• Commands: bash -n deploy/local-dev/start-dev.sh (OK); uv run --env-file .env.example python -c ... loads the whole file; a copy with the quotes stripped reproduces the truncation (None False plus a parse warning).
• Manual checks: uv run --env-file .env main.py → /health 200; uv run --env-file .env worker.py → celery ready, 6 tasks, no errors; agentic POST /v1/retrieval/query → 200 (router_used=agent_explore); new ingestion done in 5s.
• Not tested: ./deploy/local-dev/start-dev.sh — The host has enabled PostgreSQL/Redis.

Deployment Notes

• No env-var contract change: the quotes are consumed by the parser, so parsed
  values are identical. --env-file is a CLI flag, not an env var.
• No migrations, queue, storage, or release-order requirements.
• An existing local .env copied from the old template keeps the truncation until it is re-copied or quoted; self-hosted deployments are fixed by picking up the new template. No runtime code changed.
• Rollback: plain revert.

Checklist

• Tests were added or updated when behavior changed
• Public docs, examples, or OpenAPI contracts were updated when needed
• Database migrations are idempotent and safe to deploy
• Logs, errors, and validation paths avoid leaking secrets or user data
• The pull request description explains any breaking or user-visible change