fix: double-spaced code blocks on landing page (#13)

* chore(seo): improve discoverability across npm, GitHub, and search engines

- Point homepage to docs site for npm canonical link
- Add 10 keywords to package.json (nuxt3, nuxt4, vue3, typescript, etc.)
- Add 8 GitHub topics for search visibility
- Add "Why nuxt-safe-action?" section and comparison table to README
- Add TypeScript badge to README
- Expand Open Graph and Twitter Card meta on docs landing page
- Add site.url for proper sitemap and canonical tag generation
- Add robots.txt with sitemap reference
- Enrich all docs page descriptions for better meta tags

* chore: fix comparison table accuracy and bump to v0.4.1

Acknowledge useFetch, file-based server routes, and output type inference
in the $fetch column. Reframe the "Why" section around genuine
differentiators: input type safety, per-action middleware, and
field-level validation errors.

* fix: override Nuxt UI display:block on Shiki .line spans

Nuxt UI's Pre.vue sets .shiki span.line { display: block } which
combined with line-height creates double-spaced code blocks on the
landing page.

Author: rutbergphilip

docs/app/pages/index.vue

@@ -550,6 +550,10 @@ html.dark .shiki span {
   background: transparent;
 }
 
+.code-block :deep(.shiki span.line) {
+  display: inline;
+}
+
 .code-arrow {
   display: flex;
   flex-direction: column;