refactor: consolidate blockchain explorer into single app and update backup ignore patterns

- Remove standalone explorer-web app (README, HTML, package files)
- Add /web endpoint to blockchain-explorer for web interface access
- Update .gitignore to exclude application backup archives (*.tar.gz, *.zip)
- Add backup documentation files to .gitignore (BACKUP_INDEX.md, README.md)
- Consolidate explorer functionality into main blockchain-explorer application

docs/1_project/5_done.md

@@ -47,6 +47,27 @@ This document tracks components that have been successfully deployed and are ope
   - **Circuit Registry**: 3 circuit types with performance metrics and feature flags
   - **Production Deployment**: Full ZK workflow operational (compilation → witness → proof generation → verification)
 
+- ✅ **Cross-Chain Trading Exchange** - Deployed March 6, 2026
+  - **Complete Cross-Chain Exchange API** (Port 8001) with atomic swaps and bridging
+  - **Multi-Chain Database Schema** with chain isolation for orders, trades, and swaps
+  - **Real-Time Exchange Rate Calculation** with liquidity pool management
+  - **CLI Integration** with comprehensive cross-chain commands (`aitbc cross-chain`)
+  - **Security Features**: Slippage protection, atomic execution, automatic refunds
+  - **Supported Chains**: ait-devnet ↔ ait-testnet with easy expansion capability
+  - **Fee Structure**: Transparent 0.3% total fee (0.1% bridge + 0.1% swap + 0.1% liquidity)
+  - **API Endpoints**: 
+    - `/api/v1/cross-chain/swap` - Create cross-chain swaps
+    - `/api/v1/cross-chain/bridge` - Create bridge transactions
+    - `/api/v1/cross-chain/rates` - Get exchange rates
+    - `/api/v1/cross-chain/pools` - View liquidity pools
+    - `/api/v1/cross-chain/stats` - Trading statistics
+  - **CLI Commands**: 
+    - `aitbc cross-chain swap` - Create swaps with slippage protection
+    - `aitbc cross-chain bridge` - Bridge tokens between chains
+    - `aitbc cross-chain status` - Monitor transaction status
+    - `aitbc cross-chain rates` - Check exchange rates
+  - **Production Status**: Fully operational with background processing and monitoring
+
 - ✅ **Enhanced AI Agent Services Deployment** - Deployed February 2026
   - **6 New Services**: Multi-Modal Agent (8002), GPU Multi-Modal (8003), Modality Optimization (8004), Adaptive Learning (8005), Enhanced Marketplace (8006), OpenClaw Enhanced (8007)
   - **Complete CLI Tools**: 50+ commands across 5 command groups with full test coverage