Add CSV upload panel for meters and readings

- Add CSV upload service with upsert logic for meters
- Add CSV upload routes (POST /csv-upload/meters, POST /csv-upload/readings)
- Add template download endpoints for CSV format
- Create standalone upload-panel React app on port 5174
- Support concentrator_serial lookup for meter creation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

upload-panel/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "upload-panel",
+  "private": true,
+  "version": "1.0.0",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "tsc && vite build",
+    "preview": "vite preview"
+  },
+  "dependencies": {
+    "lucide-react": "^0.559.0",
+    "react": "^18.2.0",
+    "react-dom": "^18.2.0"
+  },
+  "devDependencies": {
+    "@tailwindcss/vite": "^4.1.18",
+    "@types/react": "^18.2.66",
+    "@types/react-dom": "^18.2.22",
+    "@vitejs/plugin-react": "^4.2.1",
+    "tailwindcss": "^4.1.18",
+    "typescript": "^5.2.2",
+    "vite": "^5.2.0"
+  }
+}