refactor(api): DTO-Helper extrahieren + N+1 in marketplace/decks beheben

- `lib/dto.ts`: `toDeckDto` und `toCardDto` aus routes/decks.ts und
  routes/cards.ts extrahiert — testbar, zentrale Output-Shape-Doku
- `lib/marketplace/dto.ts`: `toPublicDeckDto`, `toOwnerDto`, `toVersionDto`
  aus routes/marketplace/decks.ts extrahiert
- `GET /:slug` in marketplace/decks.ts: Version + Owner parallel per
  `Promise.all` statt sequenziell (2 RTT → 1 RTT)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/lib/dto.ts

@@ -0,0 +1,33 @@
+import { cards, decks } from '../db/schema/index.ts';
+
+export function toDeckDto(row: typeof decks.$inferSelect) {
+	return {
+		id: row.id,
+		user_id: row.userId,
+		name: row.name,
+		description: row.description,
+		color: row.color,
+		category: row.category,
+		visibility: row.visibility,
+		fsrs_settings: row.fsrsSettings,
+		content_hash: row.contentHash,
+		forked_from_marketplace_deck_id: row.forkedFromMarketplaceDeckId,
+		forked_from_marketplace_version_id: row.forkedFromMarketplaceVersionId,
+		created_at: row.createdAt.toISOString(),
+		updated_at: row.updatedAt.toISOString(),
+	};
+}
+
+export function toCardDto(row: typeof cards.$inferSelect) {
+	return {
+		id: row.id,
+		deck_id: row.deckId,
+		user_id: row.userId,
+		type: row.type,
+		fields: row.fields,
+		media_refs: row.mediaRefs ?? [],
+		content_hash: row.contentHash,
+		created_at: row.createdAt.toISOString(),
+		updated_at: row.updatedAt.toISOString(),
+	};
+}

apps/api/src/lib/marketplace/dto.ts

@@ -0,0 +1,43 @@
+import { publicDecks, publicDeckVersions } from '../../db/schema/index.ts';
+import type { AuthorRow } from '../../db/schema/marketplace/index.ts';
+
+export function toPublicDeckDto(row: typeof publicDecks.$inferSelect) {
+	return {
+		id: row.id,
+		slug: row.slug,
+		title: row.title,
+		description: row.description,
+		language: row.language,
+		category: row.category,
+		license: row.license,
+		price_credits: row.priceCredits,
+		owner_user_id: row.ownerUserId,
+		latest_version_id: row.latestVersionId,
+		is_featured: row.isFeatured,
+		is_takedown: row.isTakedown,
+		created_at: row.createdAt.toISOString(),
+	};
+}
+
+export function toOwnerDto(row: AuthorRow) {
+	return {
+		slug: row.slug,
+		display_name: row.displayName,
+		verified_mana: row.verifiedMana,
+		verified_community: row.verifiedCommunity,
+		pseudonym: row.pseudonym,
+	};
+}
+
+export function toVersionDto(row: typeof publicDeckVersions.$inferSelect) {
+	return {
+		id: row.id,
+		deck_id: row.deckId,
+		semver: row.semver,
+		changelog: row.changelog,
+		content_hash: row.contentHash,
+		card_count: row.cardCount,
+		published_at: row.publishedAt.toISOString(),
+		deprecated_at: row.deprecatedAt?.toISOString() ?? null,
+	};
+}

apps/api/src/routes/cards.ts

@@ -11,6 +11,7 @@ import {
 } from '@cards/domain';
 
 import { makeInitialReviewRows } from '../lib/reviews.ts';
+import { toCardDto } from '../lib/dto.ts';
 
 import { getDb, type CardsDb } from '../db/connection.ts';
 import { cards, decks, reviews } from '../db/schema/index.ts';
@@ -190,17 +191,3 @@ export function cardsRouter(deps: CardsDeps = {}): Hono<{ Variables: AuthVars }>
 
 	return r;
 }
-
-function toCardDto(row: typeof cards.$inferSelect) {
-	return {
-		id: row.id,
-		deck_id: row.deckId,
-		user_id: row.userId,
-		type: row.type,
-		fields: row.fields,
-		media_refs: row.mediaRefs ?? [],
-		content_hash: row.contentHash,
-		created_at: row.createdAt.toISOString(),
-		updated_at: row.updatedAt.toISOString(),
-	};
-}

apps/api/src/routes/decks.ts

@@ -7,6 +7,7 @@ import { DeckCreateSchema, DeckUpdateSchema } from '@cards/domain';
 import { getDb, type CardsDb } from '../db/connection.ts';
 import { cards, decks } from '../db/schema/index.ts';
 import { authMiddleware, type AuthVars } from '../middleware/auth.ts';
+import { toDeckDto } from '../lib/dto.ts';
 import { ulid } from '../lib/ulid.ts';
 
 /** Optional injectable DB für Tests. */
@@ -162,21 +163,3 @@ export function decksRouter(deps: DecksDeps = {}): Hono<{ Variables: AuthVars }>
 
 	return r;
 }
-
-function toDeckDto(row: typeof decks.$inferSelect) {
-	return {
-		id: row.id,
-		user_id: row.userId,
-		name: row.name,
-		description: row.description,
-		color: row.color,
-		category: row.category,
-		visibility: row.visibility,
-		fsrs_settings: row.fsrsSettings,
-		content_hash: row.contentHash,
-		forked_from_marketplace_deck_id: row.forkedFromMarketplaceDeckId,
-		forked_from_marketplace_version_id: row.forkedFromMarketplaceVersionId,
-		created_at: row.createdAt.toISOString(),
-		updated_at: row.updatedAt.toISOString(),
-	};
-}

apps/api/src/routes/marketplace/decks.ts

@@ -12,10 +12,10 @@ import {
 	publicDeckVersions,
 	publicDecks,
 } from '../../db/schema/index.ts';
-import type { AuthorRow } from '../../db/schema/marketplace/index.ts';
 import { authMiddleware, type AuthVars } from '../../middleware/auth.ts';
 import { optionalAuthMiddleware } from '../../middleware/marketplace/optional-auth.ts';
 import { moderateDeckContent } from '../../lib/marketplace/ai-moderation.ts';
+import { toPublicDeckDto, toOwnerDto, toVersionDto } from '../../lib/marketplace/dto.ts';
 import { validateSlug } from '../../lib/marketplace/slug.ts';
 import { hashVersionCards } from '../../lib/marketplace/version-hash.ts';
 
@@ -104,47 +104,6 @@ function semverGreater(a: string, b: string): boolean {
 	return false;
 }
 
-function toDeckDto(row: typeof publicDecks.$inferSelect) {
-	return {
-		id: row.id,
-		slug: row.slug,
-		title: row.title,
-		description: row.description,
-		language: row.language,
-		category: row.category,
-		license: row.license,
-		price_credits: row.priceCredits,
-		owner_user_id: row.ownerUserId,
-		latest_version_id: row.latestVersionId,
-		is_featured: row.isFeatured,
-		is_takedown: row.isTakedown,
-		created_at: row.createdAt.toISOString(),
-	};
-}
-
-function toOwnerDto(row: AuthorRow) {
-	return {
-		slug: row.slug,
-		display_name: row.displayName,
-		verified_mana: row.verifiedMana,
-		verified_community: row.verifiedCommunity,
-		pseudonym: row.pseudonym,
-	};
-}
-
-function toVersionDto(row: typeof publicDeckVersions.$inferSelect) {
-	return {
-		id: row.id,
-		deck_id: row.deckId,
-		semver: row.semver,
-		changelog: row.changelog,
-		content_hash: row.contentHash,
-		card_count: row.cardCount,
-		published_at: row.publishedAt.toISOString(),
-		deprecated_at: row.deprecatedAt?.toISOString() ?? null,
-	};
-}
-
 export function marketplaceDecksRouter(
 	deps: MarketplaceDecksDeps = {}
 ): Hono<{ Variables: Partial<AuthVars> }> {
@@ -159,7 +118,7 @@ export function marketplaceDecksRouter(
 		const [deck] = await db.select().from(publicDecks).where(eq(publicDecks.slug, slug)).limit(1);
 		if (!deck) return c.json({ error: 'not_found' }, 404);
 
-		const [versionAndOwner] = await Promise.all([
+		const [latestVersion, ownerRow] = await Promise.all([
 			deck.latestVersionId
 				? db
 						.select()
@@ -168,17 +127,13 @@ export function marketplaceDecksRouter(
 						.limit(1)
 						.then((rows) => rows[0] ?? null)
 				: Promise.resolve(null),
+			db.select().from(authors).where(eq(authors.userId, deck.ownerUserId)).limit(1)
+				.then((rows) => rows[0] ?? null),
 		]);
 
-		const [ownerRow] = await db
-			.select()
-			.from(authors)
-			.where(eq(authors.userId, deck.ownerUserId))
-			.limit(1);
-
 		return c.json({
-			deck: toDeckDto(deck),
-			latest_version: versionAndOwner ? toVersionDto(versionAndOwner) : null,
+			deck: toPublicDeckDto(deck),
+			latest_version: latestVersion ? toVersionDto(latestVersion) : null,
 			owner: ownerRow ? toOwnerDto(ownerRow) : null,
 		});
 	});
@@ -250,7 +205,7 @@ export function marketplaceDecksRouter(
 				ownerUserId: userId,
 			})
 			.returning();
-		return c.json(toDeckDto(created), 201);
+		return c.json(toPublicDeckDto(created), 201);
 	});
 
 	// PATCH /:slug — Metadaten.
@@ -290,7 +245,7 @@ export function marketplaceDecksRouter(
 			})
 			.where(and(eq(publicDecks.id, deck.id)))
 			.returning();
-		return c.json(toDeckDto(updated));
+		return c.json(toPublicDeckDto(updated));
 	});
 
 	// POST /:slug/publish — neue Version.
@@ -389,7 +344,7 @@ export function marketplaceDecksRouter(
 
 		return c.json(
 			{
-				deck: toDeckDto(result.deck),
+				deck: toPublicDeckDto(result.deck),
 				version: toVersionDto(result.version),
 				moderation: {
 					verdict: moderation.verdict,