perf: replace 1.5 MB cameleer-logo.svg refs with optimised PNGs

The Inkscape-exported cameleer-logo.svg in public/ is 1.5 MB —
loaded eagerly in the SiteHeader (32×32) and Hero (64×64), it was
the dominant hit on the homepage's largest-contentful-paint. The
relaunch's added above-the-fold DOM nudged Lighthouse perf from
0.95 to 0.92 and tipped CI's >=0.95 threshold red.

Switch all four SVG references to the pre-optimised PNG icons that
already ship in public/icons/:
  - SiteHeader (32-displayed): /icons/cameleer-48.png   (4.4 KB)
  - Hero       (64-displayed): /icons/cameleer-192.png  (36 KB)
  - SiteFooter (24-displayed): /icons/cameleer-32.png   (2.4 KB)
  - BaseLayout favicon link: drop the SVG, keep the existing
    32 PNG fallback (already declared on the next line).

Local Lighthouse (http-server, no gzip) before: perf 0.72,
LCP 10.0s. After: perf 0.94, LCP 1.6s. CI on Linux + LH static
server should comfortably clear the 0.95 gate.

The SVG file itself is left in place — unreferenced, but kept in
case any external link still points at it.

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

src/components/sections/Hero.astro

@@ -22,7 +22,7 @@ const pins: Pin[] = [
     <div class="grid lg:grid-cols-12 gap-10 lg:gap-14 items-center">
       <div class="lg:col-span-5">
         <img
-          src="/cameleer-logo.svg"
+          src="/icons/cameleer-192.png"
           width="64"
           height="64"
           alt=""