chore: update dependencies and refactor post layout

- Updated devDependencies in package.json:
  - @astrojs/check from ^0.6.0 to ^0.9.4
  - @astrojs/tailwind from ^5.1.0 to ^6.0.2
  - astro from ^4.8.2 to ^5.13.7
- Removed layout declaration from waterbase.md and yantra-launcher.md
- Refactored [slug].astro to use PostLayout for rendering posts

Author: coderGtm