Add Astro port of the logo generator

Astro page (src/pages/index.astro) renders the markup statically from
the shared src/logo.js defaults; interactivity lives in a bundled
client <script> that imports the same core (inlineTextShadow,
cssOutput) and wires the DOM — no framework runtime. Keeps the
accessibility markup (labels, aria, <details>/<summary>, focus rings)
and native <form> reset.

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

.gitignore

@@ -0,0 +1,5 @@
+node_modules
+dist
+.astro
+*.log
+.DS_Store