fix(server): return conflict for policy-blocked actions

[Gsbreddy]

Summary

Why

Changes

Validation

Run the same checks as CI (see .github/workflows/ci.yml) before opening / updating the PR:

• uv sync --frozen --extra dev
• uv run python -m ruff check src tests
• uv run python -m pytest
• uv run python scripts/generate_schemas.py then git diff --exit-code schemas/ (if models/schemas touched)
• cd web && npm ci && npm run build && cd .. && git diff --exit-code src/flightdeck/server/static/ (if web/src/ or deps changed)
• cd web && npx playwright install chromium && npm run test:e2e (if web/ changed)
• uv run flightdeck-quickstart-verify
• uv run flightdeck --help

With pip / venv only, use python -m … equivalents from DEVELOPMENT.md.

Schema / Storage Impact

• None
• Schema change
• Storage change

Risk

Review

• Requested review from maintainers (CODEOWNERS → @flightdeckdev/maintainers on the org repo). On a fork, GitHub may not auto-request; use Reviewers on the PR.
• PR is small and scoped (see AGENTS.md); linked issue or release note intent noted if helpful.

Notes