chore: remove obsolete icon assets

Remove the unused root logo and obsolete tray template SVG.

AI-assisted-by: Codex
AI-model: gpt-5.6-sol
AI-reasoning-effort: medium
Co-authored-by: Codex <codex@openai.com>

src/assets/tray-template.svg

@@ -1,6 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" width="64" height="64" viewBox="0 0 64 64">
-  <rect x="2" y="2" width="60" height="60" rx="18" fill="#22b573"/>
-  <rect x="24" y="10" width="16" height="27" rx="8" fill="#fff"/>
-  <path d="M17 30v4c0 8.3 6.7 15 15 15s15-6.7 15-15v-4M32 49v7M24 56h16"
-        fill="none" stroke="#fff" stroke-width="4" stroke-linecap="round" stroke-linejoin="round"/>
-</svg>