fix: complete remaining 8 optimization items

- HTTP connection pooling: UpstreamClient & WebsiteClient reuse httpx.Client
- Deduplicate decimal_string into shared app/utils/number.py
- Split scheduler transaction: snapshot write → webhook/website sync in separate sessions
- Remove hardcoded 170.106.100.210 migration from database.py
- Reset consecutive_failures on upstream update
- Healthcheck: install curl, replace python -c with curl -f
- Add .dockerignore to reduce build context
- Frontend: add axios-retry with exponential backoff (5xx/network errors only)

frontend/package.json

@@ -8,13 +8,14 @@
     "preview": "vite preview"
   },
   "dependencies": {
-    "vue": "^3.5.13",
-    "vue-router": "^4.4.5",
-    "pinia": "^2.2.6",
-    "element-plus": "^2.8.8",
     "@element-plus/icons-vue": "^2.3.1",
     "axios": "^1.7.9",
-    "dayjs": "^1.11.13"
+    "axios-retry": "^4.5.0",
+    "dayjs": "^1.11.13",
+    "element-plus": "^2.8.8",
+    "pinia": "^2.2.6",
+    "vue": "^3.5.13",
+    "vue-router": "^4.4.5"
   },
   "devDependencies": {
     "@vitejs/plugin-vue": "^5.2.1",