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>

.pre-commit-config.yaml

@@ -0,0 +1,28 @@
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v4.5.0
+    hooks:
+      - id: trailing-whitespace
+      - id: end-of-file-fixer
+      - id: check-yaml
+      - id: check-added-large-files
+
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.3.0
+    hooks:
+      - id: ruff
+        args: [ --fix, --exit-non-zero-on-fix ]
+        files: ^backend/
+
+  - repo: https://github.com/psf/black-pre-commit-mirror
+    rev: 24.2.0
+    hooks:
+      - id: black
+        files: ^backend/
+
+  - repo: https://github.com/pre-commit/mirrors-prettier
+    rev: v4.0.0-alpha.8
+    hooks:
+      - id: prettier
+        files: ^frontend/
+        types_or: [javascript, jsx, ts, tsx, json, css, md]