- Use existing MULTIPLIER_S/M/L from \$entities/Font in SliderArea instead
of inlining the 0.5/0.75/1 literals (constants already existed but were
duplicated at the call site).
- Centralize API base URL in \$shared/api/endpoints.ts (was duplicated
between proxyFonts and FilterAndSortFonts filters api).
- Promote every 'glyphdiff:...' localStorage key to a named module-level
STORAGE_KEY constant. Test files now import the source constant rather
than redeclaring it (eliminates silent-typo divergence risk).
Ilia Mashkov