feat: add ESLint flat config, Prettier, dependency-cruiser, and Husky

Setup code quality tooling for the monorepo:
- ESLint 9 flat config with TypeScript, import ordering, and NestJS rules
- Prettier with consistent formatting across all files
- dependency-cruiser enforcing module boundary rules (no cross-module internals, no circular deps)
- Husky + lint-staged for pre-commit hooks
- Auto-fixed existing files for type imports and import ordering

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.prettierignore

@@ -0,0 +1,5 @@
+node_modules
+dist
+.next
+coverage
+pnpm-lock.yaml