Replace logo with compacted style: dots + bold M, no connecting lines

The compacted taskbar icon (dots only, no connecting curves) looks cleaner
and more iconic than the full logo with lines, especially at larger sizes.
Adopt this as the standard logo across the entire app:

- Update mcpmux.svg to use compacted design (dots + bold M, no lines)
- Update McpMuxGlyph inline SVG component in App.tsx to match
- Regenerate all icon sizes (PNG, ICO, ICNS) from new SVG
- Update all 7 screenshots with the new title bar glyph

https://claude.ai/code/session_01J4whZ2FE8DHRZJo7tZeW5m

Author: claude