Add Svelte + Vite port of the logo generator

Svelte 5 (runes) single-component port over the shared src/logo.js
core. $state holds the model, $derived produces the generated CSS and
the logo's style string, $effect syncs the body background. bind:value
drives the controls (range/number inputs coerce to numbers). Keeps the
accessibility markup (labels, aria, <details>/<summary>, focus rings);
reset restores defaults via the form's onreset handler.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,4 @@
+node_modules
+dist
+*.log
+.DS_Store