Improve Card and CardReview inline docs

- Add documentation comments to Card and CardReview structs
- Reorder properties in Card struct, moving 'status' to the top
- Improve CardReview initializer documentation
- Remove outdated comment in CardReview

Sources/SwiftFSRS/Models/Card.swift

@@ -1,6 +1,9 @@
 import Foundation
 
 public struct Card: Hashable, Codable, Sendable {
+  /// The current state of the card (New, Learning, Review, Relearning)
+  public var status: Status
+
   /// Date when the card is next due for review
   public var due: Date
 
@@ -22,9 +25,6 @@ public struct Card: Hashable, Codable, Sendable {
   /// Times the card was forgotten or remembered incorrectly
   public var lapses: Int
 
-  /// The current state of the card (New, Learning, Review, Relearning)
-  public var status: Status
-
   /// The most recent review date, if applicable
   public var lastReview: Date?
 

Sources/SwiftFSRS/Models/CardReview.swift

@@ -1,10 +1,18 @@
 import Foundation
 
 public struct CardReview: Codable {
+  /// The post-review card.
   public var card: Card
+
+  /// The review log.
   public var reviewLog: ReviewLog
 
-  // Unlike other implementations, we only persist pre-review data in the review log
+  /// Initialize a new card review.
+  ///
+  /// - Parameters:
+  ///   - card: The post-review card.
+  ///   - oldCard: The pre-review card.
+  ///   - rating: The rating given to the card.
   public init(card: Card, oldCard: Card, rating: Rating) {
     self.card = card