feat(docs): add code comparison page with create a route example

[dreyfus92]

adds a code comparison page with the first example, create a route, for the 8 starters. one markdown file per framework under content/code-comparison/<example>/<framework>.md, every fenced block is the full file at its title= path so you can drop them into a fresh starter and it just works.

tabs use the framework logos instead of names. the logo map moved to lib/framework-logos.ts and the home cards use it too, so the light-mode css hacks are gone.

things I hit while toying with this:

• starlight's TabItem only takes a text label, so the tab strip is a tiny custom element.
• a misnamed snippet file fails astro check, so a typo won't slip through ci. a missing one just shows a placeholder tab.
• nuxt's starter has no pages/, so its snippet swaps app.vue for <NuxtPage />.

every snippet was verified by writing it into a fresh starter, running pnpm dev and hitting /about and /posts/1.

the rest of the examples from the issue can be their own issues 😄

related: #111

[43081j]

seems good to me!

i don't know enough without digging deeper to review the individual code snippets, but the overall change seems good.