feat(icon): centre and strengthen the app icon

The Wunjo rune sat left of centre and thin. It is heavier now (a 6.5
stroke), bigger, and nudged right of the geometric centre so the heavy
stave and the light flag balance about the middle of the tile — so it
reads clearly as a home-screen icon.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/static/icon.svg

@@ -1,9 +1,13 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
   <!-- Wunjo, the rune Verdande's name begins with. Drawn as strokes rather than
-       as a filled glyph so it stays legible at 16px in a browser tab. -->
+       as a filled glyph so it stays legible at 16px in a browser tab. Bigger and
+       heavier than it was, to read clearly as a home-screen icon, and nudged right
+       of the geometric centre so the heavy stave and the light flag balance about
+       the middle of the tile — a bounding box centred on 32 leaves the stave
+       looking left-hung. -->
   <rect width="64" height="64" rx="14" fill="#111312"/>
-  <g fill="none" stroke="#5fbf8f" stroke-width="4.5" stroke-linecap="round" stroke-linejoin="round">
-    <path d="M22 14v36"/>
-    <path d="M22 17l17 8-17 8"/>
+  <g fill="none" stroke="#5fbf8f" stroke-width="6.5" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M26 11v42"/>
+    <path d="M26 15l17 9.5L26 34"/>
   </g>
 </svg>