v0.3.0 — Phase β-2 Study-Loop

Voller Lern-Flow mit Web-Parität: fällige Karten via /reviews/due
laden, flip + rate (4 Buttons + Haptic), Grades via Offline-Queue
ans Server-FSRS schicken.

- Card/Review/DueReview DTOs mit snake_case + camelCase-deckId-
  Sonderfall im embedded card-Subobjekt
- CardType-Enum (alle 7 Typen), Rating-Enum mit deutschen Labels
- Cloze-Helper 1:1-Port aus cards-domain (extractClusterIds,
  subIndexCount, clusterId, renderPrompt/Answer, hint)
- CardsAPI.dueReviews(deckId:) + gradeReview(cardId,subIndex,rating,reviewedAt)
- PendingGrade SwiftData-Model + GradeQueue (FIFO-Drain, originaler
  Timestamp bleibt, bei Netzfehler in Queue, Retry beim nächsten Drain)
- StudySession @Observable State-Machine
- CardRenderer für basic, basic-reverse, cloze; Placeholder für
  image-occlusion/audio-front/typing/multiple-choice (β-3/β-4)
- RatingBar mit UIImpactFeedbackGenerator (medium/heavy)
- StudySessionView per NavigationLink aus DeckListView
- 9 neue Tests (Cloze: 8, Review-Decoding: 3), insgesamt 17 grün

Server-authoritative FSRS bleibt — kein ts-fsrs-Port.
Endurance-Test auf realem Gerät steht aus (siehe PLAN.md).

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

Sources/Core/Domain/Review.swift

@@ -0,0 +1,113 @@
+import Foundation
+
+/// Rating-Werte für `POST /reviews/:cardId/:subIndex/grade`.
+/// Aus `cards/packages/cards-domain/src/schemas/review.ts:RatingSchema`.
+enum Rating: String, Codable, Sendable, CaseIterable {
+    case again
+    case hard
+    case good
+    case easy
+
+    /// Anzeige-Label auf dem Rating-Button.
+    var label: String {
+        switch self {
+        case .again: "Nochmal"
+        case .hard: "Schwer"
+        case .good: "Gut"
+        case .easy: "Leicht"
+        }
+    }
+
+    /// Kurz-Symbol für minimalistische UI.
+    var shortcut: String {
+        switch self {
+        case .again: "1"
+        case .hard: "2"
+        case .good: "3"
+        case .easy: "4"
+        }
+    }
+}
+
+/// FSRS-Review-State. Aus `ReviewStateSchema`.
+enum ReviewState: String, Codable, Sendable {
+    case new
+    case learning
+    case review
+    case relearning
+}
+
+/// Review-DTO. Wire-Format aus `cards/apps/api/src/routes/reviews.ts:toReviewDto`.
+struct Review: Codable, Hashable, Sendable {
+    let cardId: String
+    let subIndex: Int
+    let userId: String
+    let due: Date
+    let stability: Double
+    let difficulty: Double
+    let elapsedDays: Double
+    let scheduledDays: Double
+    let learningSteps: Int
+    let reps: Int
+    let lapses: Int
+    let state: ReviewState
+    let lastReview: Date?
+
+    enum CodingKeys: String, CodingKey {
+        case cardId = "card_id"
+        case subIndex = "sub_index"
+        case userId = "user_id"
+        case due
+        case stability
+        case difficulty
+        case elapsedDays = "elapsed_days"
+        case scheduledDays = "scheduled_days"
+        case learningSteps = "learning_steps"
+        case reps
+        case lapses
+        case state
+        case lastReview = "last_review"
+    }
+}
+
+/// Eintrag aus `/reviews/due?deck_id=X` — Review + zugehörige Card.
+struct DueReview: Codable, Hashable, Sendable, Identifiable {
+    let review: Review
+    let card: ReviewCard
+
+    var id: String { "\(review.cardId)-\(review.subIndex)" }
+
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        // Flat-Decoding: Review-Felder + card-Objekt im selben JSON-Objekt
+        review = try Review(from: decoder)
+        card = try container.decode(ReviewCard.self, forKey: .card)
+    }
+
+    func encode(to encoder: Encoder) throws {
+        try review.encode(to: encoder)
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(card, forKey: .card)
+    }
+
+    enum CodingKeys: String, CodingKey {
+        case card
+    }
+}
+
+/// Wrapper-Response von `GET /api/v1/reviews/due?deck_id=X`.
+struct DueReviewsListResponse: Decodable, Sendable {
+    let reviews: [DueReview]
+    let total: Int
+}
+
+/// Body für `POST /reviews/:cardId/:subIndex/grade`.
+struct GradeReviewBody: Encodable, Sendable {
+    let rating: Rating
+    let reviewedAt: Date
+
+    enum CodingKeys: String, CodingKey {
+        case rating
+        case reviewedAt = "reviewed_at"
+    }
+}