grep -oP '.' splits multi-byte emoji into individual bytes when the
locale is not UTF-8 (e.g. CI runners with LANG=C), causing pyftsubset
to fail on invalid codepoints.
Remove redundant `font-family: sans-serif` from 18 component-level
declarations — they now inherit the Helvetica/Arial/Noto Sans stack
from the global `*` selector in app.css.
Add self-hosted NotoColorEmoji subset (56 KB, down from 11 MB) as
fallback for systems without the Noto Color Emoji font installed.
The subset is generated at prebuild time via pyftsubset with a fixed
list of the ~32 emojis actually used on the site.
