feat(swqos): add SWQOS provider blacklist configuration

- Add SWQOS_BLACKLIST constant for disabling specific providers
- Add SwqosConfig::is_blacklisted() method to check blacklist status
- Skip blacklisted providers during client initialization with warning
- Remove NextBlock references from README, README_CN and examples
- NextBlock is blacklisted by default, can be enabled by removing from SWQOS_BLACKLIST

src/lib.rs

@@ -198,6 +198,11 @@ impl TradingClient {
         let mut swqos_clients: Vec<Arc<SwqosClient>> = vec![];
 
         for swqos in swqos_configs {
+            // Check blacklist, skip disabled providers
+            if swqos.is_blacklisted() {
+                eprintln!("\u{26a0}\u{fe0f} SWQOS {:?} is blacklisted, skipping", swqos.swqos_type());
+                continue;
+            }
             match SwqosConfig::get_swqos_client(rpc_url.clone(), commitment.clone(), swqos.clone())
                 .await
             {

src/swqos/mod.rs

@@ -58,6 +58,13 @@ lazy_static::lazy_static! {
     static ref TIP_ACCOUNT_CACHE: RwLock<Vec<String>> = RwLock::new(Vec::new());
 }
 
+/// SWQOS provider blacklist configuration
+/// Providers added here will be disabled even if configured by user
+/// To enable a provider, remove it from this list
+pub const SWQOS_BLACKLIST: &[SwqosType] = &[
+    SwqosType::NextBlock,  // NextBlock is disabled by default
+];
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum TradeType {
     Create,
@@ -187,6 +194,11 @@ impl SwqosConfig {
         }
     }
 
+    /// Check if current config is in the blacklist
+    pub fn is_blacklisted(&self) -> bool {
+        SWQOS_BLACKLIST.contains(&self.swqos_type())
+    }
+
     pub fn get_endpoint(swqos_type: SwqosType, region: SwqosRegion, url: Option<String>) -> String {
         if let Some(custom_url) = url {
             return custom_url;