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/.eslintrc.json

@@ -0,0 +1 @@
+{"env":{"browser":true,"es2021":true,"node":true},"extends":["eslint:recommended","plugin:react/recommended","plugin:react-hooks/recommended","plugin:jsx-a11y/recommended"],"parserOptions":{"ecmaFeatures":{"jsx":true},"ecmaVersion":"latest","sourceType":"module"},"root":true,"rules":{"no-console":["warn",{"allow":["warn","error"]}],"no-unused-vars":["warn",{"argsIgnorePattern":"^_"}],"react/prop-types":"warn","react/react-in-jsx-scope":"off"},"settings":{"react":{"version":"detect"}}}