Initial commit: fastapi-traffic rate limiting library

- Core rate limiting with multiple algorithms (sliding window, token bucket, etc.)
- SQLite and memory backends
- Decorator and dependency injection patterns
- Middleware support
- Example usage files

fastapi_traffic/backends/__init__.py

@@ -0,0 +1,19 @@
+"""Backend implementations for rate limit storage."""
+
+from fastapi_traffic.backends.base import Backend
+from fastapi_traffic.backends.memory import MemoryBackend
+from fastapi_traffic.backends.sqlite import SQLiteBackend
+
+__all__ = [
+    "Backend",
+    "MemoryBackend",
+    "SQLiteBackend",
+]
+
+# Optional Redis backend
+try:
+    from fastapi_traffic.backends.redis import RedisBackend
+
+    __all__.append("RedisBackend")
+except ImportError:
+    pass