🔧(frontend) add telephony feature configuration from backend

Pass telephony service availability and settings to frontend to enable
conditional UI rendering based on SIP functionality status.

src/backend/core/api/__init__.py

@@ -42,6 +42,13 @@ def get_frontend_configuration(request):
             "available_modes": settings.RECORDING_WORKER_CLASSES.keys(),
             "expiration_days": settings.RECORDING_EXPIRATION_DAYS,
         },
+        "telephony": {
+            "enabled": settings.ROOM_TELEPHONY_ENABLED,
+            "phone_number": settings.ROOM_TELEPHONY_PHONE_NUMBER
+            if settings.ROOM_TELEPHONY_ENABLED
+            else None,
+            "default_country": settings.ROOM_TELEPHONY_DEFAULT_COUNTRY,
+        },
     }
     frontend_configuration.update(settings.FRONTEND_CONFIGURATION)
     return Response(frontend_configuration)

src/backend/meet/settings.py

@@ -609,6 +609,16 @@ class Base(Configuration):
         environ_name="ROOM_TELEPHONY_PIN_MAX_RETRIES",
         environ_prefix=None,
     )
+    ROOM_TELEPHONY_PHONE_NUMBER = values.Value(
+        None,
+        environ_name="ROOM_TELEPHONY_PHONE_NUMBER",
+        environ_prefix=None,
+    )
+    ROOM_TELEPHONY_DEFAULT_COUNTRY = values.Value(
+        "US",
+        environ_name="ROOM_TELEPHONY_DEFAULT_COUNTRY",
+        environ_prefix=None,
+    )
 
     # pylint: disable=invalid-name
     @property

src/frontend/src/api/useConfig.ts

@@ -30,6 +30,11 @@ export interface ApiConfig {
     available_modes?: RecordingMode[]
     expiration_days?: number
   }
+  telephony: {
+    enabled: boolean
+    phone_number?: string
+    default_country?: string
+  }
   manifest_link?: string
 }