refactor: rename ManaDeck to Cards across entire monorepo

Rename the flashcard/deck management app from ManaDeck to Cards:
- Directory: apps/manadeck → apps/cards, packages/manadeck-database → packages/cards-database
- Packages: @manadeck/* → @cards/*, @manacore/manadeck-database → @manacore/cards-database
- Domain: manadeck.mana.how → cards.mana.how
- Storage: manadeck-storage → cards-storage
- Database: manadeck → cards
- All shared packages, infra configs, services, i18n, and docs updated
- 244 files changed, zero remaining manadeck references

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared-theme/src/app-routes.ts

@@ -118,8 +118,8 @@ export const APP_ROUTES: Record<string, AppRouteConfig> = {
 		],
 	},
 
-	manadeck: {
-		appId: 'manadeck',
+	cards: {
+		appId: 'cards',
 		defaultRoute: '/decks',
 		availableRoutes: [
 			{ path: '/decks', label: 'Decks', icon: 'layers', alwaysVisible: true },

packages/shared-theme/src/store.svelte.ts

@@ -203,8 +203,8 @@ export const APP_THEME_CONFIGS = {
 			dark: '239 84% 67%' as HSLValue,
 		},
 	},
-	manadeck: {
-		appId: 'manadeck',
+	cards: {
+		appId: 'cards',
 		defaultVariant: 'ocean' as ThemeVariant,
 		primaryColor: {
 			light: '239 84% 67%' as HSLValue, // Indigo #6366f1