refactor: restructure project into muxplex/ subdir with brand integration

- Move coordinator/, frontend/, Caddyfile, pyproject.toml, requirements.txt,
  docs/ into muxplex/ subdir in prep for packaging/sharing
- Add brand assets to frontend/: favicon.ico, pwa-192/512.png,
  apple-touch-icon.png, wordmark-on-dark.svg
- Update app: title → muxplex, header → wordmark SVG, brand color tokens
  in style.css, manifest.json updated with muxplex name and brand icons
- Add design system: assets/branding/tokens.css (101 CSS custom properties),
  tokens.json (127 tokens), DESIGN-SYSTEM.md (856-line spec)
- Add assets/branding/: SVG sources, rendered PNGs (icons, favicons, PWA, OG)
- Add scripts/render-brand-assets.py for reproducible PNG generation
- Add muxplex/README.md

assets/branding/README.md

@@ -0,0 +1,40 @@
+# muxplex Brand Assets
+
+## Source files (SVGs)
+All brand assets are derived from these source SVGs in `svg/`:
+
+| File | Use |
+|------|-----|
+| `svg/icon/muxplex-icon-dark.svg` | App icon — dark background version |
+| `svg/icon/muxplex-icon-light.svg` | App icon — light background version |
+| `svg/wordmark/wordmark-on-dark.svg` | Wordmark text — for use on dark surfaces |
+| `svg/wordmark/wordmark-on-light.svg` | Wordmark text — for use on light surfaces |
+| `svg/lockup/lockup-on-dark.svg` | Icon + wordmark combined — dark |
+| `svg/lockup/lockup-on-light.svg` | Icon + wordmark combined — light |
+
+## Generated assets
+Run `../scripts/render-brand-assets.py` to regenerate everything from the SVG sources.
+
+| Directory | Contents |
+|-----------|----------|
+| `icons/` | App icons at 16–1024px |
+| `favicons/` | favicon.ico, favicon-*.png, apple-touch-icon.png |
+| `pwa/` | PWA manifest icons (192, 512px) |
+| `og/` | Open Graph images 1200×630 (dark + light) |
+| `wordmark/` | Wordmark PNGs at 32 and 64px height |
+| `lockup/` | Lockup PNGs at 32 and 64px height |
+
+## Wordmark note
+Font: Urbanist 700 (Google Fonts). SVGs reference Google Fonts CDN.
+For offline rendering, install locally: `pip install cairosvg` and ensure network access
+or embed the font in the SVG beforehand.
+
+## Colour palette
+| Token | Hex | Use |
+|-------|-----|-----|
+| Dark background | `#0D1117` | Primary dark bg |
+| Icon inner | `#10131C` | Icon card bg (dark) |
+| White / light text | `#F0F6FF` | "mux" wordmark, icon frame |
+| Cyan | `#00D9F5` | "plex" wordmark, cyan traffic light |
+| Amber | `#F1A640` | Amber traffic light, accent |
+| Light panes | `#E8E9EE` | Icon card bg (light) |