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

🤖 Generated with [Qoder][https://qoder.com]

examples/trading_client/src/main.rs

@@ -58,11 +58,10 @@ async fn create_trading_client_simple() -> AnyResult<TradingClient> {
         SwqosConfig::Helius("".to_string(), SwqosRegion::Default, None, Some(true)),
     ];
 
-    // Optional: Customize WSOL ATA and Seed optimization settings
-    let trade_config = TradeConfig::new(rpc_url, swqos_configs, commitment).with_wsol_ata_config(
-        true, // create_wsol_ata_on_startup: Check and create WSOL ATA on startup
-        true, // use_seed_optimize: Enable seed optimization for all ATA operations
-    );
+    let trade_config = TradeConfig::builder(rpc_url, swqos_configs, commitment)
+        .create_wsol_ata_on_startup(true)
+        .use_seed_optimize(true)
+        .build();
 
     // Creates new infrastructure internally
     let client = TradingClient::new(Arc::new(payer), trade_config).await;