feat: add Node1 minimum tip amount validation (0.002 SOL)

- Add intelligent tip amount detection for Node1
- Implement MIN_TIP_AMOUNT check in transaction builder
- Add MIN_TIP_AMOUNT.md documentation
- Optimize pumpswap instruction handling
- Update common utility functions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/trading/common/transaction_builder.rs

@@ -11,6 +11,7 @@ use super::{
 };
 use crate::{
     common::{nonce_cache::DurableNonceInfo, SolanaRpcClient},
+    constants::swqos::NODE1_TIP_ACCOUNTS,
     trading::{MiddlewareManager, core::transaction_pool::{acquire_builder, release_builder}},
 };
 
@@ -45,10 +46,24 @@ pub async fn build_transaction(
 
     // Add tip transfer instruction
     if with_tip && tip_amount > 0.0 {
+        // 🔧 Node1 最小小费金额限制：0.002 SOL（仅限 Node1）
+        const MIN_TIP_AMOUNT: f64 = 0.002;
+
+        // 检查是否是 Node1 的 tip_account
+        let is_node1 = NODE1_TIP_ACCOUNTS.iter().any(|&account| account == *tip_account);
+
+        let actual_tip_amount = if is_node1 && tip_amount < MIN_TIP_AMOUNT {
+            // Node1 要求最小 0.002 SOL
+            MIN_TIP_AMOUNT
+        } else {
+            // 其他 swqos 使用原始金额
+            tip_amount
+        };
+
         instructions.push(transfer(
             &payer.pubkey(),
             tip_account,
-            sol_str_to_lamports(tip_amount.to_string().as_str()).unwrap_or(0),
+            sol_str_to_lamports(actual_tip_amount.to_string().as_str()).unwrap_or(0),
         ));
     }