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-lock.json

@@ -14,6 +14,7 @@
         "dotenv": "^16.4.7",
         "ethers": "^5.8.0",
         "https-proxy-agent": "^7.0.6",
+        "undici": "^7.22.0",
         "ws": "^8.19.0"
       },
       "devDependencies": {
@@ -1828,6 +1829,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/undici": {
+      "version": "7.22.0",
+      "resolved": "https://registry.npmjs.org/undici/-/undici-7.22.0.tgz",
+      "integrity": "sha512-RqslV2Us5BrllB+JeiZnK4peryVTndy9Dnqq62S3yYRRTj0tFQCwEniUy2167skdGOy3vqRzEvl1Dm4sV2ReDg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=20.18.1"
+      }
+    },
     "node_modules/undici-types": {
       "version": "5.26.5",
       "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-5.26.5.tgz",