feat: Add comprehensive API client modules and JWT authentication to Python SDK

- Add pyjwt>=2.10.0 dependency to requirements.txt
- Add AuthProvider class with API key and JWT token support (create_token, validate_token, refresh_token, get_headers methods)
- Add APIClient base class with retry logic, error handling, and async session management
- Add SubscriberAPI module (get, list, create, update, suspend, activate, terminate methods)
- Add UsageAPI module (get_stats, list_events, get_realtime methods

sdk/python/telecom_sdk/__init__.py

@@ -1,4 +1,15 @@
 from .client import TelecomSDK
+from .auth import AuthProvider
+from .api import (
+    APIClient,
+    SubscriberAPI,
+    UsageAPI,
+    PaymentAPI,
+    RatingPlanAPI,
+    SystemAPI,
+    GraphQLAPI,
+)
+from .websocket import WebSocketClient
 from .types import (
     Subscriber,
     UsageStats,
@@ -6,25 +17,54 @@ from .types import (
     SystemStats,
     HealthStatus,
     WebSocketMessage,
+    UsageEvent,
+    RatingPlan,
+    RealTimeUsage,
+    PaginatedResponse,
 )
 from .exceptions import (
     TelecomError,
     AuthenticationError,
     APIError,
     NetworkError,
+    ValidationError,
+    RateLimitError,
+    ServerError,
 )
 
 __version__ = "1.0.0"
 __all__ = [
+    # Main SDK client
     "TelecomSDK",
+    # Authentication
+    "AuthProvider",
+    # API modules
+    "APIClient",
+    "SubscriberAPI",
+    "UsageAPI",
+    "PaymentAPI",
+    "RatingPlanAPI",
+    "SystemAPI",
+    "GraphQLAPI",
+    # WebSocket
+    "WebSocketClient",
+    # Types
     "Subscriber",
-    "UsageStats", 
+    "UsageStats",
     "PaymentTransaction",
     "SystemStats",
     "HealthStatus",
     "WebSocketMessage",
+    "UsageEvent",
+    "RatingPlan",
+    "RealTimeUsage",
+    "PaginatedResponse",
+    # Exceptions
     "TelecomError",
     "AuthenticationError",
     "APIError",
     "NetworkError",
+    "ValidationError",
+    "RateLimitError",
+    "ServerError",
 ]