feat(study): Multiple-Choice-Karten gerendert

CardRenderer für multipleChoice ist nicht mehr Placeholder. Web-
Vorbild: MultipleChoiceView.svelte.

MultipleChoiceCardView (Features/Study/):
- Lädt Distractors vom Server beim card.id-Wechsel
  (CardsAPI.distractors(deckId, cardId, field, count))
- Versucht erst field=answer, fallback field=back (für Decks mit
  basic/basic-reverse-Karten daneben)
- Fallback auf distractor_pool-Feld (newline-separated) wenn
  Deck zu klein
- 4 Optionen shuffled = [answer + 3 Distractors]
- User-Tap markiert Auswahl (kein erneutes Pick möglich)
- Vor Flip: nur Selected-Hint (primary border)
- Nach Flip: richtige = green-check, falsche-gewählte = red-cross,
  unselected richtige bleibt green-highlight
- Fallback "tooFew" (< 1 Distractor): zeigt Antwort nach Flip
  ohne Auswahl

CardsAPI.distractors → DistractorsResponse {distractors: [String]}.

Typing bleibt Placeholder — eigene UI-Pattern (Text-Input + Diff)
brauchen mehr Design-Arbeit, separate Phase.

Build 7 → 8, 35 Tests grün.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sources/Core/API/CardsAPI.swift

@@ -52,6 +52,21 @@ actor CardsAPI {
         return try decoder.decode(CardListResponse.self, from: data).cards
     }
 
+    /// `GET /api/v1/decks/:deckId/distractors` — N zufällige Feldwerte
+    /// aus anderen Karten desselben Decks. Server-Schema erlaubt nur
+    /// `front`, `back`, `answer`, `question` als field.
+    func distractors(
+        deckId: String,
+        cardId: String,
+        field: String = "answer",
+        count: Int = 3
+    ) async throws -> [String] {
+        let path = "/api/v1/decks/\(deckId)/distractors?card_id=\(cardId)&field=\(field)&count=\(count)"
+        let (data, http) = try await transport.request(path: path)
+        try ensureOK(http, data: data)
+        return try decoder.decode(DistractorsResponse.self, from: data).distractors
+    }
+
     /// `GET /api/v1/reviews/due?deck_id=...&limit=500` — Anzahl fälliger
     /// Reviews in einem Deck.
     func dueCount(deckId: String) async throws -> Int {

Sources/Core/Domain/Deck.swift

@@ -129,3 +129,8 @@ struct CardListResponse: Decodable, Sendable {
 struct DueReviewsResponse: Decodable, Sendable {
     let total: Int
 }
+
+/// Server-Response von `GET /api/v1/decks/:deckId/distractors`.
+struct DistractorsResponse: Decodable, Sendable {
+    let distractors: [String]
+}

Sources/Features/Study/CardRenderer.swift

@@ -28,7 +28,9 @@ struct CardRenderer: View {
                 imageOcclusionView
             case .audioFront:
                 audioFrontView
-            case .typing, .multipleChoice:
+            case .multipleChoice:
+                MultipleChoiceCardView(card: card, isFlipped: isFlipped)
+            case .typing:
                 placeholderView
             }
         }

Sources/Features/Study/MultipleChoiceCardView.swift

@@ -0,0 +1,199 @@
+import ManaCore
+import SwiftUI
+
+/// Multiple-Choice-Karten-View: zeigt 4 shuffled Optionen (1 richtige
+/// + 3 Distractors vom Server). User-Tap markiert Wahl, beim Flip
+/// werden richtige Antwort + Wahl hervorgehoben.
+///
+/// Web-Vorbild: `cards/apps/web/src/lib/components/MultipleChoiceView.svelte`.
+struct MultipleChoiceCardView: View {
+    let card: ReviewCard
+    let isFlipped: Bool
+
+    @Environment(AuthClient.self) private var auth
+    @State private var options: [String] = []
+    @State private var selected: String?
+    @State private var phase: LoadPhase = .loading
+
+    enum LoadPhase: Sendable {
+        case loading
+        case ready
+        case tooFew   // < 1 Distractor → manueller Modus
+        case failed
+    }
+
+    var body: some View {
+        VStack(alignment: .leading, spacing: 16) {
+            text(card.fields["front"] ?? "")
+                .font(.title3)
+                .foregroundStyle(CardsTheme.foreground)
+
+            switch phase {
+            case .loading:
+                ProgressView()
+                    .tint(CardsTheme.primary)
+                    .frame(maxWidth: .infinity)
+                    .padding(.top, 12)
+
+            case .ready:
+                ForEach(options, id: \.self) { option in
+                    optionRow(option)
+                }
+
+            case .tooFew:
+                if isFlipped {
+                    answerOnlyView
+                } else {
+                    Text("Nicht genug andere Karten im Deck für Multiple-Choice — tippe auf »Antwort anzeigen«.")
+                        .font(.caption)
+                        .foregroundStyle(CardsTheme.mutedForeground)
+                }
+
+            case .failed:
+                Text("Distractors konnten nicht geladen werden.")
+                    .font(.caption)
+                    .foregroundStyle(CardsTheme.error)
+            }
+        }
+        .frame(maxWidth: .infinity, alignment: .leading)
+        .task(id: card.id) {
+            await loadOptions()
+        }
+    }
+
+    /// Option-Row mit dynamischem Highlight: vor Flip nur Selected-Hint,
+    /// nach Flip wird richtige Antwort grün, falsche-aber-gewählte rot.
+    @ViewBuilder
+    private func optionRow(_ option: String) -> some View {
+        let isCorrect = option == card.fields["answer"]
+        let isSelected = option == selected
+
+        Button {
+            if selected == nil { selected = option }
+        } label: {
+            HStack(alignment: .top, spacing: 12) {
+                statusIcon(isCorrect: isCorrect, isSelected: isSelected)
+                    .frame(width: 22)
+                Text(option)
+                    .font(.subheadline)
+                    .foregroundStyle(CardsTheme.foreground)
+                    .multilineTextAlignment(.leading)
+                Spacer(minLength: 0)
+            }
+            .padding(.vertical, 12)
+            .padding(.horizontal, 14)
+            .background(background(isCorrect: isCorrect, isSelected: isSelected), in: RoundedRectangle(cornerRadius: 10, style: .continuous))
+            .overlay(
+                RoundedRectangle(cornerRadius: 10, style: .continuous)
+                    .stroke(border(isCorrect: isCorrect, isSelected: isSelected), lineWidth: 1)
+            )
+        }
+        .buttonStyle(.plain)
+        .disabled(isFlipped || selected != nil)
+    }
+
+    @ViewBuilder
+    private func statusIcon(isCorrect: Bool, isSelected: Bool) -> some View {
+        if isFlipped {
+            if isCorrect {
+                Image(systemName: "checkmark.circle.fill")
+                    .foregroundStyle(CardsTheme.success)
+            } else if isSelected {
+                Image(systemName: "xmark.circle.fill")
+                    .foregroundStyle(CardsTheme.error)
+            } else {
+                Image(systemName: "circle")
+                    .foregroundStyle(CardsTheme.mutedForeground.opacity(0.4))
+            }
+        } else if isSelected {
+            Image(systemName: "largecircle.fill.circle")
+                .foregroundStyle(CardsTheme.primary)
+        } else {
+            Image(systemName: "circle")
+                .foregroundStyle(CardsTheme.mutedForeground.opacity(0.4))
+        }
+    }
+
+    private func background(isCorrect: Bool, isSelected: Bool) -> Color {
+        if isFlipped {
+            if isCorrect { return CardsTheme.success.opacity(0.12) }
+            if isSelected { return CardsTheme.error.opacity(0.10) }
+            return CardsTheme.surfaceHover
+        }
+        return isSelected
+            ? CardsTheme.primary.opacity(0.10)
+            : CardsTheme.surface
+    }
+
+    private func border(isCorrect: Bool, isSelected: Bool) -> Color {
+        if isFlipped {
+            if isCorrect { return CardsTheme.success.opacity(0.55) }
+            if isSelected { return CardsTheme.error.opacity(0.55) }
+            return CardsTheme.border
+        }
+        return isSelected ? CardsTheme.primary.opacity(0.5) : CardsTheme.border
+    }
+
+    /// Fallback wenn nicht genug Distractors: zeigt die Antwort
+    /// direkt nach Flip, ohne Auswahl-Spiel.
+    private var answerOnlyView: some View {
+        VStack(alignment: .leading, spacing: 6) {
+            Divider().background(CardsTheme.border)
+            Text(card.fields["answer"] ?? "")
+                .font(.title3)
+                .foregroundStyle(CardsTheme.primary)
+                .padding(.top, 4)
+        }
+    }
+
+    private func text(_ markdown: String) -> some View {
+        let attributed = (try? AttributedString(
+            markdown: markdown,
+            options: AttributedString.MarkdownParsingOptions(
+                interpretedSyntax: .inlineOnlyPreservingWhitespace
+            )
+        )) ?? AttributedString(markdown)
+        return Text(attributed)
+            .multilineTextAlignment(.leading)
+    }
+
+    private func loadOptions() async {
+        phase = .loading
+        selected = nil
+        let api = CardsAPI(auth: auth)
+        let answer = card.fields["answer"] ?? ""
+
+        var distractors: [String] = []
+        // Erst answer-Feld versuchen, dann back-Feld als Fallback
+        // (Decks mit basic/basic-reverse-Karten daneben).
+        for field in ["answer", "back"] {
+            if distractors.count >= 3 { break }
+            if let result = try? await api.distractors(
+                deckId: card.deckId,
+                cardId: card.id,
+                field: field,
+                count: 3
+            ) {
+                let filtered = result.filter { $0 != answer && !distractors.contains($0) }
+                distractors.append(contentsOf: filtered)
+            }
+        }
+
+        // Fallback aus statischem distractor_pool-Field (Web-Pattern)
+        if distractors.count < 3, let pool = card.fields["distractor_pool"] {
+            let poolItems = pool
+                .split(separator: "\n")
+                .map { $0.trimmingCharacters(in: .whitespaces) }
+                .filter { !$0.isEmpty && $0 != answer && !distractors.contains($0) }
+            distractors.append(contentsOf: poolItems)
+        }
+
+        if distractors.isEmpty {
+            phase = .tooFew
+            return
+        }
+        let finalDistractors = Array(distractors.prefix(3))
+        options = ([answer] + finalDistractors).shuffled()
+        phase = .ready
+    }
+}

project.yml

@@ -55,7 +55,7 @@ targets:
       path: Sources/Resources/Info.plist
       properties:
         CFBundleShortVersionString: "0.1.0"
-        CFBundleVersion: "7"
+        CFBundleVersion: "8"
         CFBundleDevelopmentRegion: de
         CFBundleDisplayName: Cardecky
         LSApplicationCategoryType: "public.app-category.education"
@@ -111,7 +111,7 @@ targets:
       properties:
         CFBundleDisplayName: Als Karte speichern
         CFBundleShortVersionString: "0.1.0"
-        CFBundleVersion: "7"
+        CFBundleVersion: "8"
         NSExtension:
           NSExtensionPointIdentifier: com.apple.share-services
           NSExtensionPrincipalClass: $(PRODUCT_MODULE_NAME).ShareViewController
@@ -144,7 +144,7 @@ targets:
       properties:
         CFBundleDisplayName: Cardecky Widget
         CFBundleShortVersionString: "0.1.0"
-        CFBundleVersion: "7"
+        CFBundleVersion: "8"
         NSExtension:
           NSExtensionPointIdentifier: com.apple.widgetkit-extension
     entitlements: