feat(env): update .gitignore and package files for Convex integration

- Added .env.staging files for admin and storefront applications to .gitignore.
- Updated package.json and package-lock.json to include @convex-dev/resend and its dependencies.
- Introduced new Convex-related modules and updated peer dependencies for better compatibility.

This commit enhances the environment configuration and integrates the Resend service into the project.

package.json

@@ -22,6 +22,7 @@
   },
   "dependencies": {
     "@clerk/backend": "^2.32.1",
+    "@convex-dev/resend": "^0.2.3",
     "@tailwindcss/postcss": "^4.2.0",
     "convex": "^1.32.0",
     "next": "16.1.6",