chore(config,manifest): Update start script with PORT environment variable and theme color to white

- Update start script to accept PORT environment variable with default fallback to 3000
- Change manifest theme color from teal (#00d4aa) to white (#ffffff) for consistent branding
- Align theme configuration with recent accent color updates across the application

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "dev": "next dev --turbopack",
     "build": "next build",
-    "start": "next start",
+    "start": "next start -p ${PORT:-3000}",
     "lint": "eslint",
     "db:generate": "drizzle-kit generate",
     "db:push": "drizzle-kit push",