Refactor layout and navigation components; remove theme toggler

- Updated layout.tsx to remove the ThemeProvider and directly include Analytics, SpeedInsights, and Navigation components.
- Removed ThemeToggler component from Navigation.
- Adjusted global CSS to use media queries for dark theme styles instead of data attributes.
- Cleaned up package.json by removing the next-themes dependency.

next-env.d.ts

@@ -2,4 +2,4 @@
 /// <reference types="next/image-types/global" />
 
 // NOTE: This file should not be edited
-// see https://nextjs.org/docs/app/building-your-application/configuring/typescript for more information.
+// see https://nextjs.org/docs/app/api-reference/config/typescript for more information.