feat: add undici dependency + dynamic gas multiplier for tx retry

- Install undici package for fetch proxy support
- Add gas multiplier on retry to handle "replacement transaction underpriced"
  - Attempt 1: 1x gas
  - Attempt 2: 2x gas
  - Attempt 3: 4x gas

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -36,6 +36,7 @@
     "dotenv": "^16.4.7",
     "ethers": "^5.8.0",
     "https-proxy-agent": "^7.0.6",
+    "undici": "^7.22.0",
     "ws": "^8.19.0"
   },
   "devDependencies": {