Add flashcards feature with spaced repetition scheduling

Adds a full flashcards system: FSRS-based scheduling, cloze/basic
card types, CSV import/export, media storage, and study UI, wired
into navigation and the dashboard alongside existing question flows.

api/QuestionsApi/Services/DashboardStore.cs

@@ -1,5 +1,6 @@
 using MongoDB.Driver;
 using QuestionsApi.Models;
+using QuestionsApi.Services.Flashcards;
 
 namespace QuestionsApi.Services;
 
@@ -15,8 +16,15 @@ public sealed class DashboardStore
     private readonly IMongoCollection<UserNotepad> _notes;
     private readonly QuestionStore _questions;
     private readonly ReviewQueueStore _reviewQueue;
+    private readonly FlashcardStudyService _flashcards;
+    private readonly FlashcardScheduleStore _flashcardSchedules;
 
-    public DashboardStore(MongoDatabaseProvider mongo, QuestionStore questions, ReviewQueueStore reviewQueue)
+    public DashboardStore(
+        MongoDatabaseProvider mongo,
+        QuestionStore questions,
+        ReviewQueueStore reviewQueue,
+        FlashcardStudyService flashcards,
+        FlashcardScheduleStore flashcardSchedules)
     {
         _attempts = mongo.Database.GetCollection<QuestionAttempt>("QuestionAttempts");
         _ratings = mongo.Database.GetCollection<UserRating>("UserRatings");
@@ -28,6 +36,8 @@ public sealed class DashboardStore
         _notes = mongo.Database.GetCollection<UserNotepad>("UserNotepads");
         _questions = questions;
         _reviewQueue = reviewQueue;
+        _flashcards = flashcards;
+        _flashcardSchedules = flashcardSchedules;
     }
 
     public async Task<DashboardResponse> GetAsync(string userId, DateTime nowUtc)
@@ -45,8 +55,10 @@ public sealed class DashboardStore
         var bookmarkCountTask = _bookmarks.CountDocumentsAsync(value => value.UserId == userId);
         var notepadTask = _notes.Find(value => value.UserId == userId).FirstOrDefaultAsync();
         var reviewAttemptsTask = _reviewQueue.GetReviewsSinceAsync(userId, weekStart);
+        var flashcardCountsTask = _flashcards.GetDashboardCountsAsync(userId, nowUtc, weekStart);
+        var flashcardReviewsTask = _flashcardSchedules.GetReviewsSinceAsync(userId, weekStart);
         await Task.WhenAll(attemptsTask, ratingTask, ccsRatingTask, ccsAttemptsTask, completedCcsCountTask,
-            simulationsTask, bookmarkCountTask, notepadTask, reviewAttemptsTask);
+            simulationsTask, bookmarkCountTask, notepadTask, reviewAttemptsTask, flashcardCountsTask, flashcardReviewsTask);
 
         var attempts = attemptsTask.Result;
         var answeredAttempts = attempts.Where(value => !value.IsSkip).ToList();
@@ -71,7 +83,10 @@ public sealed class DashboardStore
             QuestionsThisWeek = answeredAttempts.Count(value => value.CreatedUtc >= weekStart),
             BookmarkCount = checked((int)bookmarkCountTask.Result),
             NoteCount = CountNotes(notepadTask.Result?.Content),
-            MissedQuestionCount = checked((int)pendingReviewCount)
+            MissedQuestionCount = checked((int)pendingReviewCount),
+            FlashcardsDue = flashcardCountsTask.Result.Due,
+            FlashcardsNewAvailable = flashcardCountsTask.Result.NewAvailable,
+            FlashcardsReviewedThisWeek = flashcardCountsTask.Result.ReviewedThisWeek
         };
 
         response.PerformanceTrend = Enumerable.Range(0, 30).Select(offset =>
@@ -115,12 +130,14 @@ public sealed class DashboardStore
                     + dailyCcs.Sum(CcsDurationSeconds)
                     + dailySimulations.Sum(value => value.Responses.Sum(item => Math.Max(0, item.ElapsedSeconds)))
                     + reviewAttemptsTask.Result.Where(value => value.CreatedUtc.Date == date).Sum(value => value.DurationSeconds)
+                    + flashcardReviewsTask.Result.Where(value => value.ReviewedUtc.Date == date).Sum(value => value.DurationSeconds)
             };
         }).ToList();
         response.StudyTimeSecondsThisWeek = response.WeeklyActivity.Sum(value => value.StudyTimeSeconds);
         var activeDates = attempts.Select(value => value.CreatedUtc.Date)
             .Concat(completedCcs.Select(value => value.CompletedUtc!.Value.Date))
-            .Concat(simulations.Where(value => value.CompletedUtc.HasValue).Select(value => value.CompletedUtc!.Value.Date));
+            .Concat(simulations.Where(value => value.CompletedUtc.HasValue).Select(value => value.CompletedUtc!.Value.Date))
+            .Concat(flashcardReviewsTask.Result.Select(value => value.ReviewedUtc.Date));
         response.CurrentStreak = CalculateCurrentStreak(activeDates, today);
         response.RecentActivity = await BuildRecentActivityAsync(answeredAttempts, questionMap, completedCcs, simulations);
         return response;