Bring the tighten-ui brand treatment into new-ui:
- Replace the emoji book (📚) in the sidebar header with the book-open
icon rendered in the theme accent color, matching the tighten-ui
header brand (templates/header.templ).
- Add web/static/favicon.svg (book-open glyph, tokyo-night accent
#7aa2f7 stroke) and reference it from the <head> of all 27 page
templates, so the favicon is present on login/setup/error pages too.
- Regenerate templ output for all affected templates.
