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.

package.json

@@ -0,0 +1,35 @@
+{
+  "name": "mermix",
+  "version": "0.1.0",
+  "description": "Cross-platform Mermaid diagram editor & viewer with Git-backed projects",
+  "type": "module",
+  "scripts": {
+    "dev": "vite",
+    "build": "svelte-check --tsconfig ./tsconfig.json && vite build",
+    "preview": "vite preview",
+    "check": "svelte-check --tsconfig ./tsconfig.json",
+    "tauri": "tauri",
+    "app:dev": "tauri dev",
+    "app:build": "tauri build"
+  },
+  "dependencies": {
+    "@codemirror/commands": "^6.6.0",
+    "@codemirror/language": "^6.10.2",
+    "@codemirror/state": "^6.4.1",
+    "@codemirror/view": "^6.28.0",
+    "@tauri-apps/api": "^2.0.0",
+    "@tauri-apps/plugin-dialog": "^2.0.0",
+    "codemirror": "^6.0.1",
+    "mermaid": "^11.2.0"
+  },
+  "devDependencies": {
+    "@sveltejs/vite-plugin-svelte": "^4.0.0",
+    "@tauri-apps/cli": "^2.0.0",
+    "@tsconfig/svelte": "^5.0.4",
+    "svelte": "^5.1.0",
+    "svelte-check": "^4.0.0",
+    "tslib": "^2.7.0",
+    "typescript": "^5.6.0",
+    "vite": "^5.4.0"
+  }
+}