[WIP] Add proposal detail edit flow and supporting service layer

[Copilot]

• Understand the repository structure and existing implementation
• Run tests to identify issues
• Fix missing Dict import in service/stream_type_service.py
• Verify all 50 tests pass
• Request code review
• Run security checks

Original prompt

Feature: Proposal detail edit + ProposalService, CSRF, tests

This PR implements the Proposal detail edit flow and supporting service layer.

Summary of changes:

• Add service/proposal_service.py with update_proposal that maps and persists user-editable fields.
• Convert templates/proposal_detail.html into an edit POST form and include csrf_token().
• Implement POST handling in route/proposal_route.py to construct ProposalUpdateRequest and call ProposalService.update_proposal.
• Add tests/unit/test_proposal_update.py to exercise the edit path and assert DB changes.
• Add flash rendering to templates/proposals.html and include CSRF hidden inputs in approve form.
• Disable CSRF in tests (tests/conftest.py) for now to simplify test execution.
• Add specs/004-proposal-edit/README.md documenting the feature and next steps.

Test status:

• All unit tests pass locally: 50 passed.

Notes for reviewers:

• Stage 2 items remain (integration test for edit->approve, optional server-side validation).
• CSRF is enabled in the app, but disabled in test config for simplicity; we can add test-side token handling if you prefer.

Please review and I can follow up with integration tests or stricter validation as requested.

Created from VS Code via the GitHub Pull Request extension.

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