P1: Use the Muster product logo consistently everywhere

[jusso-dev]

Goal

Use the supplied Muster shield/tree logo everywhere product identity appears. Remove every placeholder M mark and stale icon.

Scope

• Sidebar/workspace switcher.
• Login and authentication surfaces.
• PWA manifest, favicon and Apple touch icon.
• Offline/loading surfaces where a mark appears.
• README and documentation assets.
• Accessible alt text and suitable raster sizes.

Acceptance criteria

• Source scan finds no placeholder product logo or manually rendered M mark.
• Logo renders cleanly for 16, 32, 48, 96, 192 and 512 px uses.
• PWA metadata validates and standalone window uses correct icon.
• Dark/light surfaces preserve contrast without glow or gradient.
• README uses approved branding and current product image.

Verification

• Manifest/icon automated checks.
• Login, room shell and mobile screenshots.
• Exact asset/reference scan.

[jusso-dev]

Implemented on main in b89979b. The supplied shield/tree master now drives exact 16, 32, 48, 96, 180, 192, and 512 px PNG assets; favicon/shortcut/Apple/PWA metadata, shell, login, offline, README, and documentation use the approved mark. Added dimension, stale-reference, manifest, HTTP icon, head metadata, and cross-browser rendering checks. Refreshed login, room, and mobile screenshots plus the README product image. Verified lint, strict typecheck, all unit tests, production build, 4/4 browser branding checks, and screenshot generation.