feat: new polygon peony logo + updated OG image

- Replace logo partial with faceted low-poly peony bloom (v7: blush→heat)
- Update static/logo.svg (app icon, no background)
- Regenerate OG default image with new logo and correct tagline
- Update favicons

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

layouts/partials/nav.html

@@ -11,7 +11,7 @@
   >
     <!-- Logotype -->
     <a href="/" class="logo-glitch flex items-center gap-3 hover:opacity-90 transition-opacity" aria-label="{{ .Site.Params.logoText }} Home">
-      {{- partial "logo.html" (dict "id" "nav" "class" "h-8 w-auto flex-shrink-0") -}}
+      {{- partial "logo.html" (dict "id" "nav" "class" "h-10 w-auto flex-shrink-0") -}}
       <span class="font-display text-2xl md:text-3xl leading-none tracking-wide">
         {{- .Site.Params.logoText -}}
       </span>