fix: Resolve React Query compatibility issue by downgrading to React 18

- Downgrade React from v19 to v18.3.1 for better library compatibility
- Fix QueryClientProvider "createContext" error that was preventing app startup
- Update @types/react and @types/react-dom to match React 18
- Remove unused React imports to clean up TypeScript warnings

This resolves the critical runtime error:
"Cannot read properties of undefined (reading 'createContext')"

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: vchaindz

package-lock.json

@@ -32,17 +32,17 @@
     "comlink": "^4.4.2",
     "date-fns": "^4.1.0",
     "lucide-react": "^0.544.0",
-    "react": "^19.1.1",
-    "react-dom": "^19.1.1",
+    "react": "^18.3.1",
+    "react-dom": "^18.3.1",
     "react-router-dom": "^7.9.1",
     "recharts": "^3.2.1",
     "sql.js": "^1.13.0",
     "tailwind-merge": "^3.3.1"
   },
   "devDependencies": {
     "@eslint/js": "^9.35.0",
-    "@types/react": "^19.1.13",
-    "@types/react-dom": "^19.1.9",
+    "@types/react": "^18.3.24",
+    "@types/react-dom": "^18.3.7",
     "@vitejs/plugin-react": "^5.0.2",
     "autoprefixer": "^10.4.21",
     "better-sqlite3": "^12.2.0",