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

dev/cli/mock_server_8002.py

@@ -0,0 +1,17 @@
+import uvicorn
+from fastapi import FastAPI
+
+app = FastAPI()
+
+@app.get('/blockchain/status')
+async def blockchain_status():
+    return {
+        'status': 'connected',
+        'height': 12345,
+        'hash': '0x1234567890abcdef',
+        'timestamp': '2026-03-04T17:10:00Z',
+        'tx_count': 678
+    }
+
+if __name__ == '__main__':
+    uvicorn.run(app, host='127.0.0.1', port=8002)