feat: Convert to pure Astro CSS (no Tailwind)

- Removed Tailwind CSS dependency (19KB → 8.7KB CSS)
- Created native Astro CSS with CSS custom properties
- All utility classes using vanilla CSS
- Scoped component styles with Astro's built-in scoping
- Same green theme and design preserved
- Zero build dependencies for CSS
- Faster builds, smaller bundle
- True 'Astro way' of styling

node_modules/.vite/deps/_metadata.json

@@ -1,25 +1,25 @@
 {
-  "hash": "d42f017f",
+  "hash": "fd60062d",
   "configHash": "af375ec6",
-  "lockfileHash": "ff2d2eea",
-  "browserHash": "41bf6e33",
+  "lockfileHash": "11a770e9",
+  "browserHash": "c023f09e",
   "optimized": {
     "astro > cssesc": {
       "src": "../../cssesc/cssesc.js",
       "file": "astro___cssesc.js",
-      "fileHash": "e8d02241",
+      "fileHash": "f41579f9",
       "needsInterop": true
     },
     "astro > aria-query": {
       "src": "../../aria-query/lib/index.js",
       "file": "astro___aria-query.js",
-      "fileHash": "6f05959a",
+      "fileHash": "42c60d91",
       "needsInterop": true
     },
     "astro > axobject-query": {
       "src": "../../axobject-query/lib/index.js",
       "file": "astro___axobject-query.js",
-      "fileHash": "84d4262b",
+      "fileHash": "e645e7bb",
       "needsInterop": true
     }
   },