fix(identity): update KAVA address validation to EVM format

KAVA now uses EVM-compatible 0x addresses instead of Cosmos bech32 format.
DST continues to use Cosmos bech32 format (dst1...).

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

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

backend/services/identity-service/src/domain/entities/wallet-address.entity.ts

@@ -273,10 +273,12 @@ export class WalletAddress {
   private static validateAddress(chainType: ChainType, address: string): boolean {
     switch (chainType) {
       case ChainType.KAVA:
-      case ChainType.DST:
-        return /^(kava|dst)1[a-z0-9]{38}$/.test(address);
       case ChainType.BSC:
+        // KAVA 和 BSC 都使用 EVM 地址格式
         return /^0x[a-fA-F0-9]{40}$/.test(address);
+      case ChainType.DST:
+        // DST 使用 Cosmos bech32 格式
+        return /^dst1[a-z0-9]{38}$/.test(address);
       default:
         return false;
     }