feat: add Tailwind CSS and PostCSS configuration

- Created postcss.config.js to configure PostCSS with Tailwind CSS and Autoprefixer.
- Updated svelte.config.js to enable PostCSS preprocessing.
- Added tailwind.config.js for Tailwind CSS configuration.
- Updated yarn.lock to include new dependencies for Tailwind CSS, PostCSS, and related plugins.

package.json

@@ -21,10 +21,12 @@
         "@babel/core": "^7.27.7",
         "@babel/preset-env": "^7.27.2",
         "@tsconfig/svelte": "^5.0.4",
+        "autoprefixer": "^10.4.21",
         "browser-sync": "^3.0.4",
         "chokidar": "^4.0.3",
         "connect-history-api-fallback": "^2.0.0",
         "esbuild": "^0.25.5",
+        "esbuild-postcss": "^0.0.4",
         "esbuild-svelte": "^0.9.3",
         "http-proxy-middleware": "^3.0.5",
         "less": "^4.3.0",
@@ -37,6 +39,7 @@
         "svelte-check": "^4.2.2",
         "svelte-preprocess": "^6.0.3",
         "svelte-preprocess-esbuild": "^3.0.1",
+        "tailwindcss": "^3.4.16",
         "tslib": "^2.8.1",
         "typescript": "^5.8.3"
     },