chore: add project configs, backend repair services, docs, and code quality tooling

- Add pre-commit hooks (ruff, black, prettier) and ESLint/Prettier configs
- Add backend repair services (execution, orchestration, preview) with tests
- Add project documentation (CLAUDE.md, README.md, design specs and plans)
- Add MissingTagsInlinePanel component for exception handling
- Add pyproject.toml with ruff/black configuration

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/.prettierrc

@@ -0,0 +1 @@
+{"arrowParens":"always","bracketSpacing":true,"endOfLine":"lf","printWidth":100,"semi":true,"singleQuote":true,"tabWidth":2,"trailingComma":"es5"}