Lay the Almanacka design foundation: tokens, type, shell

New token system in global.css (near-white surfaces, one ink-blue
accent, no sub-12px type), self-hosted Schibsted Grotesk, rewritten
primitives (buttons, fields, modal shell, segmented, disclosure,
skeleton), a borderless 56px header with an SV | EN language toggle,
an Icon component replacing glyphs, page skeletons that keep the
layout during loading, and leave-type colours moved out of TS into
CSS variables. Feature blocks keep their structure for later phases.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

frontend/src/i18n/sv/common.ts

@@ -4,6 +4,7 @@ export const common = {
   'common.close': 'Stäng',
   'common.delete': 'Ta bort',
   'common.deleting': 'Tar bort…',
+  'common.loading': 'Laddar',
   'common.loadingEllipsis': 'Laddar…',
   'common.save': 'Spara',
   'common.saving': 'Sparar…',
@@ -13,6 +14,9 @@ export const common = {
   'leaveType.unknown': 'Okänd',
   'leaveType.vacation': 'Semester',
   'nav.calendar': 'Kalender',
+  'nav.languageAria': 'Språk',
+  'nav.languageEn': 'English',
+  'nav.languageSv': 'Svenska',
   'nav.logout': 'Logga ut',
   'nav.logoutAria': 'Logga ut',
   'nav.overview': 'Översikt',