Add pre-commit hooks for linting and formatting

Set up pre-commit framework with ruff (backend) and ESLint/Prettier/tsc
(frontend) hooks to catch issues locally before CI. Auto-format all
frontend files with Prettier to comply with the new check.

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

frontend/src/api/client.ts

@@ -10,10 +10,7 @@ export class ApiError extends Error {
   }
 }
 
-async function request<T>(
-  path: string,
-  options?: RequestInit,
-): Promise<T> {
+async function request<T>(path: string, options?: RequestInit): Promise<T> {
   const res = await fetch(`${API_BASE}/api/v1${path}`, {
     ...options,
     headers: {
@@ -52,6 +49,5 @@ export const api = {
       body: JSON.stringify(body),
     }),
 
-  del: <T = void>(path: string) =>
-    request<T>(path, { method: 'DELETE' }),
+  del: <T = void>(path: string) => request<T>(path, { method: 'DELETE' }),
 }