Refactor WhatsApp: instances call manager hub instead of Meta directly

Instances no longer hold WhatsApp API credentials. They send messages
via the el-captain-manager messaging hub API using MESSAGING_HUB_URL
and MESSAGING_HUB_KEY env vars. The hub handles Meta Graph API calls,
rate limiting, and delivery tracking centrally.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/services.php

@@ -42,4 +42,9 @@
         'webhook_verify_token' => env('WHATSAPP_WEBHOOK_VERIFY_TOKEN', ''),
     ],
 
+    'messaging_hub' => [
+        'url' => env('MESSAGING_HUB_URL', ''),
+        'key' => env('MESSAGING_HUB_KEY', ''),
+    ],
+
 ];

docker/entrypoint.sh

@@ -17,7 +17,7 @@ chmod -R 775 storage bootstrap/cache
 
 # Build .env from Docker env vars (CapRover passes them as container env)
 : > .env
-env | grep -E "^(APP_|DB_|LOG_|SESSION_|CACHE_|QUEUE_|FILESYSTEM_|BROADCAST_|MAIL_|TRUSTED_|BCRYPT_|PLATFORM_|ADMIN_|ACADEMY_|RUN_|WHATSAPP_)" | sort | sed 's/=\(.*\)/="\1"/' >> .env
+env | grep -E "^(APP_|DB_|LOG_|SESSION_|CACHE_|QUEUE_|FILESYSTEM_|BROADCAST_|MAIL_|TRUSTED_|BCRYPT_|PLATFORM_|ADMIN_|ACADEMY_|RUN_|WHATSAPP_|MESSAGING_)" | sort | sed 's/=\(.*\)/="\1"/' >> .env
 
 # Ensure APP_KEY line exists (key:generate needs it to write to)
 if ! grep -q '^APP_KEY=' .env 2>/dev/null; then