feat: integrate Muyue logo (icon embedded in Windows binary + web favicon)

Logo dropped at project root by user. Bake it everywhere it matters:

Assets:
- assets/muyue.ico — multi-res (16/24/32/48/64/128/256) generated via PIL
- assets/muyue-{16,32,64,128,256,512}.png — clean PNG resizes
- LogoMuyue.png kept at root as the source of truth

Windows binary (.exe):
- CI runs `rsrc -ico assets/muyue.ico -arch {amd64,arm64} -o cmd/muyue/rsrc_windows_{amd64,arm64}.syso`
  before `go build` (both ci-main.yml and ci-develop.yml)
- Go automatically links *.syso files matching the target GOOS/GOARCH —
  no code change in the cmd/muyue main package
- .syso files are gitignored: regenerated at every build, never committed
- Existing install-shortcuts subcommand already uses IconLocation =
  "$exe,0" so the embedded icon flows automatically into Desktop +
  Start Menu .lnk files

Web UI:
- web/public/favicon-{16,32}.png + muyue.png + muyue-64.png
- web/index.html: real <link rel="icon"> tags (16/32 PNG + apple-touch),
  replacing the placeholder SVG hexagon
- App.jsx header: 22×22 logo image rendered next to the "MUYUE" wordmark
  (rounded 4px corners for visual consistency with the source logo)

Install snippet (ci-main.yml changelog template):
- Idempotent first line: `New-Item -ItemType Directory -Force -Path $dest`
  to handle the case where the user re-runs after a partial install

Versioning unchanged (still v0.7.3 — these additions stay on the same
release branch / PR #9).

web/src/components/App.jsx

@@ -103,6 +103,7 @@ export default function App() {
     <div className="app-layout">
       <header className="header">
         <div className="header-brand">
+          <img src="/muyue-64.png" alt="Muyue" className="header-logo-img" width="22" height="22" style={{ borderRadius: 4, verticalAlign: 'middle' }} />
           <span className="header-logo">MUYUE</span>
           <span className="header-version">v{info.version || '...'}</span>
         </div>