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/cards-database/src/client.ts

@@ -10,10 +10,10 @@ let pgClient: ReturnType<typeof postgres> | null = null;
  * Get the database URL from environment variables
  */
 function getDatabaseUrl(): string {
-	const url = process.env.DATABASE_URL || process.env.MANADECK_DATABASE_URL;
+	const url = process.env.DATABASE_URL || process.env.CARDS_DATABASE_URL;
 	if (!url) {
 		throw new Error(
-			'Database URL not found. Set DATABASE_URL or MANADECK_DATABASE_URL environment variable.'
+			'Database URL not found. Set DATABASE_URL or CARDS_DATABASE_URL environment variable.'
 		);
 	}
 	return url;

packages/cards-database/src/index.ts

@@ -1,4 +1,4 @@
-// Main entry point for @manacore/manadeck-database
+// Main entry point for @manacore/cards-database
 
 // Export database client utilities
 export { createClient, getDb, closeDb, type Database } from './client.js';

packages/cards-database/src/migrate-from-supabase.ts

@@ -96,7 +96,7 @@ async function migrateTable<T>(
 }
 
 async function main() {
-	console.log('=== ManaDeck Data Migration ===');
+	console.log('=== Cards Data Migration ===');
 	console.log('From: Supabase');
 	console.log('To: PostgreSQL (Drizzle)');
 	console.log('==============================\n');