feat(server): add study session API with FSRS integration

Implement study endpoints for spaced repetition learning:
- GET /api/decks/:deckId/study to fetch due cards
- POST /api/decks/:deckId/study/:cardId to submit reviews
- Integrate ts-fsrs library for scheduling algorithm
- Add ReviewLog repository for tracking review history

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/server/repositories/review-log.ts b/src/server/repositories/review-log.ts
new file mode 100644
index 0000000..c8950d6
--- /dev/null
+++ b/src/server/repositories/review-log.ts
@@ -0,0 +1,32 @@
+import { db } from "../db/index.js";
+import { reviewLogs } from "../db/schema.js";
+import type { ReviewLog, ReviewLogRepository } from "./types.js";
+
+export const reviewLogRepository: ReviewLogRepository = {
+	async create(data: {
+		cardId: string;
+		userId: string;
+		rating: number;
+		state: number;
+		scheduledDays: number;
+		elapsedDays: number;
+		durationMs?: number | null;
+	}): Promise<ReviewLog> {
+		const [reviewLog] = await db
+			.insert(reviewLogs)
+			.values({
+				cardId: data.cardId,
+				userId: data.userId,
+				rating: data.rating,
+				state: data.state,
+				scheduledDays: data.scheduledDays,
+				elapsedDays: data.elapsedDays,
+				durationMs: data.durationMs ?? null,
+			})
+			.returning();
+		if (!reviewLog) {
+			throw new Error("Failed to create review log");
+		}
+		return reviewLog;
+	},
+};