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-lock.json

@@ -24,6 +24,7 @@
         "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"
@@ -4293,6 +4294,22 @@
         "node": ">= 0.8.0"
       }
     },
+    "node_modules/prettier": {
+      "version": "3.7.4",
+      "resolved": "https://registry.npmjs.org/prettier/-/prettier-3.7.4.tgz",
+      "integrity": "sha512-v6UNi1+3hSlVvv8fSaoUbggEM5VErKmmpGA7Pl3HF8V6uKY7rvClBOJlH6yNwQtfTueNkGVpOv/mtWL9L4bgRA==",
+      "dev": true,
+      "license": "MIT",
+      "bin": {
+        "prettier": "bin/prettier.cjs"
+      },
+      "engines": {
+        "node": ">=14"
+      },
+      "funding": {
+        "url": "https://github.com/prettier/prettier?sponsor=1"
+      }
+    },
     "node_modules/pretty-format": {
       "version": "27.5.1",
       "resolved": "https://registry.npmjs.org/pretty-format/-/pretty-format-27.5.1.tgz",