P0: scaffold Vite + Vue 3 + Tauri v2

- pnpm + TS + Tailwind 3 + Pinia + Vue Router with hash history
- 6 placeholder views (Status, Peers, Routes, Messages, Topics, Settings)
  rendered via lucide-icon sidebar in App.vue
- Tauri v2: shell, store, log, dialog plugins; bundle targets deb +
  appimage; sidecar wired via externalBin = binaries/mycelium
- scripts/fetch-mycelium.sh pins v0.6.1, maps musl asset onto
  gnu target triple expected by Tauri bundler
- CI: pnpm typecheck + cargo fmt/clippy/test

.gitignore

@@ -12,9 +12,9 @@ dist-ssr
 *.local
 
 # Tauri
-/app/src-tauri/target
-/app/src-tauri/binaries/mycelium*
-/app/src-tauri/gen/schemas
+/src-tauri/target
+/src-tauri/binaries/mycelium-*
+/src-tauri/gen
 
 # Editor / OS
 .DS_Store