refactor: Migrate to API endpoint and use real DB connection

This commit shifts the application's data fetching mechanism from local storage mocks to a dedicated API endpoint. It also refactors the database connection logic to utilize a connection pool for improved performance and scalability.

Key changes include:
- Disabling `FORCE_LOCAL_DB` in `mockDb.ts` and implementing a generic `request` function for API calls.
- Centralizing authentication headers in `mockDb.ts`.
- Modifying `server/db.js` to use `pg` and `mysql2/promise` pools and a unified `executeQuery` function.
- Updating `server/server.js` to use the database pool for queries.
- Configuring Vite's development server to proxy API requests to the backend.

vite.config.ts

@@ -1,7 +1,16 @@
+
 import { defineConfig } from 'vite'
 import react from '@vitejs/plugin-react'
 
 // https://vitejs.dev/config/
 export default defineConfig({
   plugins: [react()],
-})
+  server: {
+    proxy: {
+      '/api': {
+        target: 'http://localhost:3001',
+        changeOrigin: true,
+      },
+    },
+  },
+})