resolving some typo error

Signed-off-by: supersonicwisd1 <supersonicwisdom@gmail.com>

src/pyfed/storage/__init__.py

@@ -7,7 +7,7 @@
 # - Storage provider protocol
 # """
 
-from .base import SQLStorageBackend
+from .base import StorageBackend
 # from .backends.postgresql import PostgreSQLStorage
 # from .backends.mongodb import MongoDBStorageBackend
 # from .backends.redis import RedisStorageBackend
@@ -33,7 +33,7 @@ from .base import SQLStorageBackend
 #     'sqlite': SQLiteStorage
 # }
 
-def get_storage_backend(backend_type: str) -> type[SQLStorageBackend]:
+def get_storage_backend(backend_type: str) -> type[StorageBackend]:
     """Get storage backend class by type."""
     if backend_type not in STORAGE_BACKENDS:
         raise ValueError(f"Unknown storage backend: {backend_type}")

src/pyfed/utils/exceptions.py

@@ -143,3 +143,7 @@ class IntegrationError(ActivityPubException):
 class MiddlewareError(ActivityPubException):
     """Raised when middleware-related errors occur."""
     pass
+
+class ConfigError(ActivityPubException):
+    """Raised when configuration-related errors occur."""
+    pass
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