Add CI quality checks

[LRriver]

Summary

• Add GitHub Actions CI for frontend and backend checks on main and dev.
• Configure Ruff linting/format checks and a pytest coverage baseline.
• Document local development check commands in both English and Chinese READMEs.

Validation

• ruff check api src tests main.py
• ruff format --check api src tests main.py
• python -m pytest --cov=api --cov=src --cov-report=term-missing
• npm ci
• npm run lint
• npm run test
• npm run build

Notes

• The initial Python coverage gate is set to 45%, matching the current tested baseline of 46.23%.
• Real model API calls are intentionally excluded from default CI because they require private keys and depend on external service availability.
• npm audit is not included as a blocking CI step yet because the existing dependency tree currently reports known vulnerabilities that should be handled in a separate dependency-upgrade pass.

[gemini-code-assist]

Code Review

This pull request introduces development check documentation in the README files, adds a pyproject.toml configuration for Ruff and pytest, introduces a requirements-dev.txt file, and applies code formatting across the codebase. Feedback from the review highlights critical issues in the FastAPI routes, specifically potential temporary file leaks in api/routes/edit.py and event loop blocking caused by synchronous I/O operations in both api/routes/edit.py and api/routes/export.py. The reviewer recommends running these synchronous operations in a separate thread using asyncio.to_thread and restructuring the cleanup logic to ensure temporary files are always deleted.

Important

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