feat(observability): log Meta Graph API version at startup

Both API and Worker now emit a ✅ info log at boot showing the active
META_GRAPH_API_VERSION, or a ⚠️ warn if the version is below v21.0
(which signals a likely-deprecated version). Visible directly in
Railway logs without digging into the code.

apps/api/src/index.ts

@@ -13,6 +13,15 @@ async function start() {
         await server.listen({ port, host });
         logger.info(`🚀 API Gateway running on http://${host}:${port}`);
 
+        // Meta Graph API version observability
+        const metaVersion = process.env.META_GRAPH_API_VERSION || 'v22.0';
+        const versionNum = parseInt(metaVersion.replace(/\D/g, ''), 10);
+        if (versionNum < 21) {
+            logger.warn(`⚠️  [META] Graph API version is ${metaVersion} — likely DEPRECATED (< v21.0). Set META_GRAPH_API_VERSION to v22.0 or later to restore messaging_limit_tier.`);
+        } else {
+            logger.info(`✅ [META] Graph API version: ${metaVersion}`);
+        }
+
         startCleanupCron();
     } catch (err) {
         logger.error({ err });

apps/whatsapp-worker/src/index.ts

@@ -256,6 +256,15 @@ const start = async () => {
     try {
         await server.listen({ port: PORT, host: '0.0.0.0' });
         logger.info(`🚀 WhatsApp Worker + Bridge listening on port ${PORT}`);
+
+        // Meta Graph API version observability
+        const metaVersion = process.env.META_GRAPH_API_VERSION || 'v22.0';
+        const versionNum = parseInt(metaVersion.replace(/\D/g, ''), 10);
+        if (versionNum < 21) {
+            logger.warn(`⚠️  [META] Graph API version is ${metaVersion} — likely DEPRECATED (< v21.0). Update META_GRAPH_API_VERSION.`);
+        } else {
+            logger.info(`✅ [META] Graph API version: ${metaVersion}`);
+        }
         
         // Start the daily cron scheduler + token expiry monitor
         const { startDailyScheduler, startTokenExpiryMonitor, startWalletAlertMonitor, startWeeklyReportScheduler, startMonthlyReportScheduler, startPedagogyAdvisor } = await import('./scheduler');