feat(brand): V-viewfinder 3a — the approved rebrand (was: split-W)

The V-viewfinder was approved during the favicon-v2 picker at
/v2/, then deployed prematurely (e7b9756) and reverted (81effca) after
the 'design pick is not a deploy command' lesson. Deploying it now with
explicit go-ahead.

Files: yellow V outline with the Camogli harbor visible inside, navy
field outside. Replaces the split-W (two Vs forming a W) across:
- favicon-16/32/64
- apple-touch-icon (180)
- icon-192 + icon-512 manifest icons
- icon-512-maskable (V at 65% safe zone)
- favicon.svg vector
- favicon.ico multi-res
- root-level apple-touch-icon{,-precomposed}.png for iOS fallback paths

Cache-bust query bumped to ?v=20260515-vviewfinder so browsers refetch.

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

frontend/public/manifest.webmanifest

@@ -11,19 +11,19 @@
   "theme_color": "#fdf6ee",
   "icons": [
     {
-      "src": "/build/icons/icon-192.png?v=20260515-3a",
+      "src": "/build/icons/icon-192.png?v=20260515-vviewfinder",
       "sizes": "192x192",
       "type": "image/png",
       "purpose": "any"
     },
     {
-      "src": "/build/icons/icon-512.png?v=20260515-3a",
+      "src": "/build/icons/icon-512.png?v=20260515-vviewfinder",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "any"
     },
     {
-      "src": "/build/icons/icon-512-maskable.png?v=20260515-3a",
+      "src": "/build/icons/icon-512-maskable.png?v=20260515-vviewfinder",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "maskable"