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/i18n/en/settings.ts

@@ -21,7 +21,6 @@ export const settings = {
   'parentBalance.dubbeldagarLeftLabel': 'Dubbeldagar left (0-60)',
   'parentBalance.invalid': 'The total (sjukpenningnivå + lägstanivå) can\'t exceed {total} days.',
   'parentBalance.lagstaLeftLabel': 'Lägstanivå (minimum-rate tier) left (0-90)',
-  'parentBalance.loadingBalance': 'Loading balance…',
   'parentBalance.presetButton': 'No days taken yet',
   'parentBalance.rangeError': 'Enter a number between {min} and {max}.',
   'parentBalance.reservedExceedsError': 'Reserved days can\'t exceed the sjukpenningnivå + lägstanivå days left.',
@@ -32,6 +31,7 @@ export const settings = {
   'parentBalance.savingButton': 'Saving…',
   'parentBalance.sjukpenningLeftLabel': 'Sjukpenningnivå (income-based tier) left (0-390)',
   'parentBalance.summary': '= {left} of {total} days left',
+  'parentBalance.summaryDubbeldagar': '{count} dubbeldagar left',
   'parentBalance.title': '{name}\'s days left',
   'parentBalance.titleSelf': 'Your days left',
   'parentProfileInput.employed': 'Employed',
@@ -70,7 +70,6 @@ export const settings = {
   'settings.languageEnglishOption': 'English',
   'settings.languageLabel': 'Välj språk / Select language',
   'settings.languageSwedishOption': 'Svenska',
-  'settings.loading': 'Loading settings...',
   'settings.membersLoading': 'Loading members…',
   'settings.noChildSelected': 'No child selected yet.',
   'settings.partnerActionErrorNotFound': 'Could not find the partner. Reload the page and try again.',
@@ -112,15 +111,9 @@ export const settings = {
   'settings.title': 'Settings',
   'settings.vacationHelp': 'Enter vacation days per year. In the first year you are usually home more and have fewer days to spend on vacation, while later years have your full annual allotment. This controls how much time the planner has to work with.',
   'settings.youBadge': '(You)',
-  'vacationDaysList.empty': 'No vacation days registered.',
-  'vacationDaysList.itemDays': '{count} days',
-  'vacationDaysList.loading': 'Loading vacation days…',
-  'vacationDaysList.savedSuffix': '(+{count} saved)',
   'vacationDaysTable.assumedBadge': 'Assumed',
   'vacationDaysTable.assumedPrompt': 'No value is recorded for this year — the statutory 25 days has been assumed. Confirm or edit below.',
   'vacationDaysTable.empty': 'No years to show yet.',
-  'vacationDaysTable.saveButton': 'Save',
   'vacationDaysTable.savedDaysHeader': 'Saved days carried in',
   'vacationDaysTable.vacationDaysHeader': 'Vacation days',
-  'vacationDaysTable.yearHeader': 'Year',
 } as const