chore(mobile): check:env script lints .env.local against .env.example

apps/mobile/package.json

@@ -15,7 +15,8 @@
     "typecheck": "tsc --noEmit",
     "test": "vitest run",
     "test:watch": "vitest",
-    "clean": "rm -rf .expo node_modules/.cache .turbo *.tsbuildinfo"
+    "clean": "rm -rf .expo node_modules/.cache .turbo *.tsbuildinfo",
+    "check:env": "node scripts/check-env.mjs"
   },
   "dependencies": {
     "@babel/runtime": "^7.29.2",

apps/mobile/scripts/check-env.mjs

@@ -0,0 +1,38 @@
+#!/usr/bin/env node
+// Compares apps/mobile/.env.example with .env.local. Surfaces missing keys
+// so an onboarding dev doesn't ship a build that white-screens.
+
+import { existsSync, readFileSync } from 'node:fs';
+import { dirname, resolve } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const here = dirname(fileURLToPath(import.meta.url));
+const mobileRoot = resolve(here, '..');
+const examplePath = resolve(mobileRoot, '.env.example');
+const localPath = resolve(mobileRoot, '.env.local');
+
+if (!existsSync(localPath)) {
+  console.error('No .env.local found at ' + localPath);
+  console.error('Copy .env.example to .env.local and fill in values.');
+  process.exit(1);
+}
+
+function keysOf(path) {
+  return new Set(
+    readFileSync(path, 'utf8')
+      .split('\n')
+      .map((line) => line.trim())
+      .filter((line) => line.length > 0 && !line.startsWith('#'))
+      .map((line) => line.split('=', 1)[0]),
+  );
+}
+
+const exampleKeys = keysOf(examplePath);
+const localKeys = keysOf(localPath);
+const missing = [...exampleKeys].filter((k) => !localKeys.has(k));
+
+if (missing.length > 0) {
+  console.error('Missing keys in .env.local: ' + missing.join(', '));
+  process.exit(1);
+}
+console.log('env-ok: all .env.example keys present in .env.local');