refactor: restructure event handling from trait objects to enum pattern

- Convert UnifiedEvent from trait object (Box<dyn UnifiedEvent>) to concrete enum type
  - Remove match_event! macro in favor of native match expressions
  - Simplify event metadata access: event.event_type() -> event.metadata().event_type
  - Unify event callback signatures: Fn(Box<dyn UnifiedEvent>) -> Fn(UnifiedEvent)
  - Update all example code to use the new enum-based event system
  - Optimize type system to reduce runtime overhead and improve type safety

  Affected scope:
  - Core event parser and processor
  - All protocol event definitions (PumpFun, PumpSwap, Bonk, Raydium series, etc.)
  - gRPC and Shred streaming modules
  - All example code

src/streaming/grpc/mod.rs

@@ -12,6 +12,5 @@ pub use types::*;
 
 // 从公用模块重新导出
 pub use crate::streaming::common::{
-    BackpressureConfig, BackpressureStrategy, ConnectionConfig, MetricsManager, PerformanceMetrics,
-    StreamClientConfig as ClientConfig,
+    ConnectionConfig, MetricsManager, PerformanceMetrics, StreamClientConfig as ClientConfig,
 };