fix: overhaul PWA icons with v2 suffix to bust all cache layers

- Redesign favicon SVG with gradient border matching splash screen
- Rename all icon files with -v2 suffix to bypass browser/SW/PWA caches
- Delete 9 old/duplicate icon files (~13MB removed)
- Add nginx cache-control headers for icons and manifest
- Rename assets-cache to assets-cache-v2 to orphan stale SW cache
- Update all HTML, manifest, and component icon references

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

neode-ui/public/assets/img/l484-icon.svg

@@ -1,17 +0,0 @@
-<svg width="285" height="273" viewBox="0 0 285 273" fill="none" xmlns="http://www.w3.org/2000/svg">
-<g filter="url(#filter0_d_145_9)">
-<path d="M67.6045 215.234H154.772V240.824H28L77.7109 127.559L131.736 76.2861L67.6045 215.234ZM198.893 146.688H256.594L213.508 240.824H171.984V172.604H114.283L156.588 76.7314L177.74 50.3652L198.893 24V146.688ZM198.893 214.361L217.207 172.604H198.893V214.361ZM153.67 146.688H171.984V104.929L153.67 146.688Z" fill="white"/>
-</g>
-<defs>
-<filter id="filter0_d_145_9" x="0" y="0" width="284.594" height="272.824" filterUnits="userSpaceOnUse" color-interpolation-filters="sRGB">
-<feFlood flood-opacity="0" result="BackgroundImageFix"/>
-<feColorMatrix in="SourceAlpha" type="matrix" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 127 0" result="hardAlpha"/>
-<feOffset dy="4"/>
-<feGaussianBlur stdDeviation="14"/>
-<feComposite in2="hardAlpha" operator="out"/>
-<feColorMatrix type="matrix" values="0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.25 0"/>
-<feBlend mode="normal" in2="BackgroundImageFix" result="effect1_dropShadow_145_9"/>
-<feBlend mode="normal" in="SourceGraphic" in2="effect1_dropShadow_145_9" result="shape"/>
-</filter>
-</defs>
-</svg>