Replace react-intl with next-intl and consolidate lang files.

Migrate i18n from react-intl to next-intl, eliminating the formatjs
compilation pipeline. Translation files now live as nested JSON in
public/intl/messages/ (single source of truth), removing the duplicated
src/lang/ directory and the copy/compile build steps. The useMessages()
hook API is preserved so all 195+ consumer components are unchanged.

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

Author: mikecao

next.config.ts

@@ -1,6 +1,9 @@
 import 'dotenv/config';
+import createNextIntlPlugin from 'next-intl/plugin';
 import pkg from './package.json' with { type: 'json' };
 
+const withNextIntl = createNextIntlPlugin('./src/i18n/request.ts');
+
 const TRACKER_SCRIPT = '/script.js';
 
 const basePath = process.env.BASE_PATH || '';
@@ -164,7 +167,7 @@ if (cloudMode) {
 }
 
 /** @type {import('next').NextConfig} */
-export default {
+export default withNextIntl({
   reactStrictMode: false,
   env: {
     basePath,
@@ -202,4 +205,4 @@ export default {
   async redirects() {
     return [...redirects];
   },
-};
+});

package.json

@@ -11,7 +11,7 @@
   },
   "type": "module",
   "scripts": {
-    "dev": "next dev -p 3001 --turbo",
+    "dev": "next dev -p 3003 --turbo",
     "build": "npm-run-all check-env build-db check-db build-tracker build-geo build-app",
     "start": "next start",
     "build-docker": "npm-run-all build-db build-tracker build-geo build-app",
@@ -23,7 +23,7 @@
     "build-components": "tsup",
     "build-tracker": "rollup -c rollup.tracker.config.js",
     "build-prisma-client": "node scripts/build-prisma-client.js",
-    "build-lang": "npm-run-all format-lang compile-lang download-country-names download-language-names clean-lang",
+    "build-lang": "npm-run-all download-country-names download-language-names",
     "build-geo": "node scripts/build-geo.js",
     "build-db": "npm-run-all build-db-client build-prisma-client",
     "build-db-schema": "prisma db pull",
@@ -33,12 +33,6 @@
     "check-db": "node scripts/check-db.js",
     "check-env": "node scripts/check-env.js",
     "copy-db-files": "node scripts/copy-db-files.js",
-    "extract-messages": "formatjs extract \"src/components/messages.ts\" --out-file build/extracted-messages.json",
-    "merge-messages": "node scripts/merge-messages.js",
-    "generate-lang": "npm-run-all extract-messages merge-messages",
-    "format-lang": "node scripts/format-lang.js",
-    "compile-lang": "formatjs compile-folder --ast build/messages public/intl/messages",
-    "clean-lang": "prettier --write ./public/intl/**/*.json",
     "download-country-names": "node scripts/download-country-names.js",
     "download-language-names": "node scripts/download-language-names.js",
     "change-password": "node scripts/change-password.js",
@@ -102,6 +96,7 @@
     "lucide-react": "^0.543.0",
     "maxmind": "^5.0.5",
     "next": "^16.1.6",
+    "next-intl": "^4.8.2",
     "node-fetch": "^3.2.8",
     "npm-run-all": "^4.1.5",
     "papaparse": "^5.5.3",
@@ -111,7 +106,6 @@
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
     "react-error-boundary": "^4.0.4",
-    "react-intl": "^7.1.14",
     "react-resizable-panels": "^4.6.0",
     "react-simple-maps": "^2.3.0",
     "react-use-measure": "^2.0.4",
@@ -127,7 +121,6 @@
   },
   "devDependencies": {
     "@biomejs/biome": "^2.3.14",
-    "@formatjs/cli": "^4.2.29",
     "@netlify/plugin-nextjs": "^5.15.7",
     "@rollup/plugin-alias": "^5.0.0",
     "@rollup/plugin-commonjs": "^25.0.4",
@@ -143,7 +136,6 @@
     "babel-plugin-react-compiler": "19.1.0-rc.2",
     "cross-env": "^10.1.0",
     "cypress": "^13.6.6",
-    "extract-react-intl-messages": "^4.1.1",
     "husky": "^9.1.7",
     "jest": "^29.7.0",
     "lint-staged": "^16.2.6",