Refactor styles and remove Tailwind configuration

- Deleted postcss.config.mjs as it is no longer needed.
- Updated Layout.astro to reference main.css instead of using @tailwind components.
- Modified expressive-code.css to include a reference to Tailwind CSS.
- Reworked main.css to use @import for Tailwind and added custom variants and utilities.
- Updated markdown.css to reference main.css and adjusted anchor styles.
- Enhanced photoswipe.css and scrollbar.css with Tailwind references and applied important modifiers.
- Updated transition.css to include Tailwind reference.
- Removed tailwind.config.cjs as part of the cleanup.

src/styles/photoswipe.css

@@ -1,12 +1,14 @@
+@reference "tailwindcss";
+
 .pswp__button {
-    @apply transition bg-black/40 hover:bg-black/50 active:bg-black/60 flex items-center justify-center mr-0 w-12 h-12 !important;
+    @apply transition! bg-black/40! hover:bg-black/50! active:bg-black/60! flex! items-center! justify-center! mr-0! w-12! h-12!;
 }
 .pswp__button--zoom, .pswp__button--close {
-    @apply mt-4 rounded-xl active:scale-90 !important;
+    @apply mt-4! rounded-xl! active:scale-90!;
 }
 .pswp__button--zoom {
-    @apply mr-2.5 !important;
+    @apply mr-2.5!;
 }
 .pswp__button--close {
-    @apply mr-4 !important;
+    @apply mr-4!;
 }