chore: scaffold Tauri 2 + Svelte 5 workspace

Standard Tauri layout with a Svelte 5 + TypeScript + Vite frontend and a
Rust backend in src-tauri. Adds build tooling, app/window config,
capabilities, generated icons and the project README.

public/mermix.svg

@@ -0,0 +1,21 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" width="256" height="256">
+  <defs>
+    <linearGradient id="g" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0" stop-color="#a78bfa"/>
+      <stop offset="1" stop-color="#7c5cff"/>
+    </linearGradient>
+  </defs>
+  <rect width="256" height="256" rx="56" fill="#171a21"/>
+  <g fill="none" stroke="url(#g)" stroke-width="14" stroke-linecap="round" stroke-linejoin="round">
+    <rect x="48" y="40" width="72" height="44" rx="10"/>
+    <rect x="136" y="40" width="72" height="44" rx="10"/>
+    <rect x="92" y="160" width="72" height="44" rx="10"/>
+    <path d="M84 84 L128 160"/>
+    <path d="M172 84 L128 160"/>
+  </g>
+  <g fill="url(#g)">
+    <circle cx="84" cy="84" r="9"/>
+    <circle cx="172" cy="84" r="9"/>
+    <circle cx="128" cy="160" r="9"/>
+  </g>
+</svg>