Add Prettier for TypeScript formatting

- Install prettier
- Configure .prettierrc.json and .prettierignore
- Add npm scripts: format, format:check
- Add Makefile target: format-frontend
- Format all frontend files

frontend/package.json

@@ -11,7 +11,9 @@
     "test:e2e": "playwright test",
     "generate-api-types": "openapi-typescript http://localhost:8000/openapi.json -o app/generated/api.ts",
     "lint": "eslint .",
-    "lint:fix": "eslint . --fix"
+    "lint:fix": "eslint . --fix",
+    "format": "prettier --write .",
+    "format:check": "prettier --check ."
   },
   "dependencies": {
     "bech32": "^2.0.0",
@@ -30,6 +32,7 @@
     "eslint-plugin-react-hooks": "^7.0.1",
     "jsdom": "^26.0.0",
     "openapi-typescript": "^7.10.1",
+    "prettier": "^3.7.4",
     "typescript": "5.9.3",
     "typescript-eslint": "^8.50.0",
     "vitest": "^2.1.8"