feat: add APK_TABS environment variable for configurable tabs

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

lib/constants.ts

@@ -6,3 +6,7 @@ export const AUTH_PASSWORD = process.env.AUTH_PASSWORD || 'changeme';  // Change
 export const COOKIE_NAME = 'auth';
 export const COOKIE_MAX_AGE = 86400; // 24 hours
 export const AUTH_COOKIE_VALUE = 'ok';
+export const APK_TABS = (process.env.APK_TABS || 'dev,sandbox')
+  .split(',')
+  .map(t => t.trim())
+  .filter(Boolean);