feat: add global MEV protection and refactor TradeConfig to builder pattern

- Add `mev_protection: bool` to `TradeConfig` and `InfrastructureConfig` (default: false)
  - Astralane QUIC: switches to port 9000 (MEV-protected endpoint) when enabled
  - BlockRazor HTTP: uses `mode=sandwichMitigation` query param when enabled
  - BlockRazor gRPC: uses `mode=sandwichMitigation` when enabled
- Add `SWQOS_ENDPOINTS_ASTRALANE_QUIC_MEV` constants (port 9000) to `constants/swqos.rs`
- Fix `astralane_quic.rs` IP candidates to use the actual port from the address (supports both 7000 and 9000)
- Refactor `TradeConfig` to builder pattern via `TradeConfig::builder()`
  - Introduce `TradeConfigBuilder` with all optional fields and clear defaults
  - `TradeConfig::new()` kept as a shortcut (calls `builder().build()`) for backward compatibility
  - Remove old `with_wsol_ata_config` / `with_check_min_tip` / `with_swqos_cores_from_end` / `with_mev_protection` chain methods
- Update all 16 examples to use `TradeConfig::builder()` with commented-out options so users can discover all available settings at a glance
- Update README.md and README_CN.md code snippets to use builder pattern

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README.md

@@ -141,11 +141,14 @@ let swqos_configs: Vec<SwqosConfig> = vec![
     ), // QUIC
 ];
 // Create TradeConfig instance
-let trade_config = TradeConfig::new(rpc_url, swqos_configs, commitment);
-
-// Optional: customize WSOL ATA and seed optimization
-// let trade_config = TradeConfig::new(rpc_url, swqos_configs, commitment)
-//     .with_wsol_ata_config(true, true);  // create_wsol_ata_on_startup, use_seed_optimize
+let trade_config = TradeConfig::builder(rpc_url, swqos_configs, commitment)
+    // .create_wsol_ata_on_startup(true)  // default: true  - check & create WSOL ATA on init
+    // .use_seed_optimize(true)            // default: true  - seed optimization for ATA ops
+    // .log_enabled(true)                  // default: true  - SDK timing / SWQOS logs
+    // .check_min_tip(false)               // default: false - filter SWQOS below min tip
+    // .swqos_cores_from_end(false)        // default: false - bind SWQOS to last N CPU cores
+    // .mev_protection(false)              // default: false - MEV protection (Astralane port 9000 / BlockRazor sandwichMitigation)
+    .build();
 
 // Create TradingClient
 let client = TradingClient::new(Arc::new(payer), trade_config).await;