Fix: finish the logo redraw across every surface

[SandObserver]

Summary

• Draw the empty-dashboard mark from the logo sprite symbol in --label-primary ink and the theme accent, and remove brand-mark.js with its hard-coded #F2F2F7 strokes.
• Replace the two inline logo paths in the Settings sidebar and About hero with <use href="#sy-solid-logo">.
• Swap the traced paths in templates/icon.svg, icon-light.svg and icon-dark.svg for the favicon geometry, keeping each file's plate and placement.
• Render favicon-maskable.png as a full-bleed #0D1117 square with the logo inside the 80% safe zone, instead of a copy of favicon-512.png.
• Remove the fractions comment above logoIcon().

Testing
All green, including e2e and the Docker build. Added tests that decode the maskable PNG and check its opaque background outside the safe zone; measure painted logo and docs-icon bounds with arcs and round ends; check one accent part per docs icon; and pin the favicon and Unraid icons to the logoIcon() geometry.

Changelog

Fixed

• Show the whole logo on the empty dashboard in the light theme.
• Fill the Android home screen icon to its edges instead of leaving transparent corners.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.