Finish the redesign's edges: auth page, modals, dead code, docs

The sign-in page becomes a plain centred column with the brand mark
and a segmented login/register switch, modals lose their last inner
boxes, the red-days list collapses every year but the current one,
and the retired components' CSS, an unused list component and 23
unreferenced translation keys are removed. ARCHITECTURE.md documents
the Almanacka styling conventions and the per-year balance rule.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XBRLomdLK9jF7wU7a8AA6H

frontend/src/utils/leaveTypes.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest'
-import { getColorForType, getInkForType, getLabelForType, getTypeKey, getTypeModifier } from './leaveTypes'
+import { getColorForType, getInkForType, getLabelForType, getTypeKey } from './leaveTypes'
 import { translate } from '@/i18n'
 
 describe('getColorForType', () => {
@@ -44,18 +44,6 @@ describe('getTypeKey', () => {
   })
 })
 
-describe('getTypeModifier', () => {
-  it('returns a type-* modifier suffix for each known type', () => {
-    expect(getTypeModifier('vacation')).toBe('type-vacation')
-    expect(getTypeModifier('sjukpenning')).toBe('type-sjukpenning')
-    expect(getTypeModifier('lagsta')).toBe('type-lagsta')
-  })
-
-  it('returns type-unknown for an unknown type', () => {
-    expect(getTypeModifier('something-else')).toBe('type-unknown')
-  })
-})
-
 describe('getLabelForType', () => {
   const t = (key: Parameters<typeof translate>[1]) => translate('sv', key)
 

frontend/src/utils/leaveTypes.ts

@@ -36,15 +36,6 @@ export function getTypeKey(type: string): LeaveTypeKey {
   return isKnownType(type) ? type : 'unknown'
 }
 
-/**
- * The older `type-*` prefixed modifier, still used by the dashboard's year
- * timeline (`year-timeline__band--type-lagsta`); the calendar has moved to
- * `getTypeKey`.
- */
-export function getTypeModifier(type: string): string {
-  return `type-${getTypeKey(type)}`
-}
-
 /**
  * Localized label for a leave-day type. Takes `t` rather than importing
  * `useTranslation` itself — this is a plain utility function (not a