feat: unify UI components, AppSlider, and login screens across apps

SUMMARY:
Consolidate shared UI components into @manacore/shared-ui and add
AppSlider to all login screens for a consistent Mana ecosystem experience.

CHANGES:

1. UI Components Migration:
   - Added Card.svelte to @manacore/shared-ui with variants (elevated, outlined, ghost)
   - Migrated Manacore (7 files) and Manadeck (7 files) to use shared-ui
   - Removed local ui/ directories from both apps (8 components total)

2. AppSlider Unification:
   - Created shared AppSlider in @manacore/shared-ui with configurable props
   - Props: apps[], title, isDark, statusLabels, comingSoonLabel, openAppLabel, onAppClick
   - Supports both i18n and static text configurations
   - Updated Memoro AppSlider to use shared component with svelte-i18n
   - Updated Manacore AppSlider to use shared component
   - Created new AppSlider for ManaDeck and Märchenzauber

3. Login Page Enhancements:
   - Extended LoginPage in @manacore/shared-auth-ui with new snippets:
     - appSlider: Renders AppSlider at bottom (initial mode only)
     - headerControls: Renders controls (theme toggle, etc.) top-right
   - Updated all app login pages to include AppSlider:
     - ManaCore: indigo theme (#6366f1)
     - ManaDeck: violet theme (#8b5cf6)
     - Märchenzauber: pink theme (#FF6B9D)

4. Subscription Page Consolidation:
   - Created SubscriptionPage component in @manacore/shared-subscription-ui
   - Moved subscription data (plans, packages, costs) to shared package
   - Reduced subscription page code from ~100 to ~18 lines per app

FILES CHANGED:
- packages/shared-ui: Added Card, AppSlider, updated exports
- packages/shared-auth-ui: Extended LoginPage with snippets
- packages/shared-subscription-ui: Added SubscriptionPage, data files
- manacore/web: Migrated 7 files to shared-ui, updated login
- manadeck/web: Migrated 7 files to shared-ui, added AppSlider, updated login
- maerchenzauber/web: Added AppSlider, updated login
- memoro/web: Updated AppSlider to use shared component

DELETED (moved to shared packages):
- manacore/web/src/lib/components/ui/* (3 files)
- manadeck/web/src/lib/components/ui/* (5 files)
- memoro/web/src/lib/data/*.json (3 files)
- Various pnpm-lock.yaml and pnpm-workspace.yaml files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

packages/shared-auth-ui/src/pages/LoginPage.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import type { Component } from 'svelte';
+	import type { Component, Snippet } from 'svelte';
 	import type { AuthResult } from '../types';
 	import Icon from '../components/Icon.svelte';
 	import GoogleSignInButton from '../components/GoogleSignInButton.svelte';
@@ -36,6 +36,10 @@
 		lightBackground?: string;
 		/** Dark background color */
 		darkBackground?: string;
+		/** AppSlider snippet to render at the bottom (optional) */
+		appSlider?: Snippet;
+		/** Header snippet for controls like theme toggle and language selector */
+		headerControls?: Snippet;
 	}
 
 	let {
@@ -52,7 +56,9 @@
 		successRedirect = '/dashboard',
 		registerPath = '/register',
 		lightBackground = '#f5f5f5',
-		darkBackground = '#121212'
+		darkBackground = '#121212',
+		appSlider,
+		headerControls
 	}: Props = $props();
 
 	let loading = $state(false);
@@ -163,6 +169,13 @@
 	class="flex min-h-screen flex-col justify-between"
 	style="background-color: {getPageBackground()};"
 >
+	<!-- Header Controls (Theme Toggle, Language Selector, etc.) -->
+	{#if headerControls}
+		<div class="absolute right-4 top-4 z-50 flex items-center gap-3 opacity-60">
+			{@render headerControls()}
+		</div>
+	{/if}
+
 	<!-- Top Section - Logo -->
 	<div class="flex flex-col items-center justify-center pt-16 pb-8">
 		<div
@@ -433,6 +446,13 @@
 		</div>
 	</div>
 
-	<!-- Bottom padding -->
-	<div class="pb-8"></div>
+	<!-- App Slider (shown on initial mode) -->
+	{#if appSlider && mode === 'initial'}
+		<div class="w-full pb-8 px-2 pt-4">
+			{@render appSlider()}
+		</div>
+	{:else}
+		<!-- Bottom padding -->
+		<div class="pb-8"></div>
+	{/if}
 </div>