feat(shared): define types (User, Deck, Card, ReviewLog)

Add TypeScript type definitions for core data models used across client
and server. Types are consistent with Drizzle schema defined in server.

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

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

2 files changed, 80 insertions, 1 deletions

diff --git a/pkgs/shared/src/index.ts b/pkgs/shared/src/index.ts
index cb0ff5c..2f88e30 100644
--- a/pkgs/shared/src/index.ts
+++ b/pkgs/shared/src/index.ts
@@ -1 +1 @@
-export {};
+export * from "./types/index.js";
diff --git a/pkgs/shared/src/types/index.ts b/pkgs/shared/src/types/index.ts
new file mode 100644
index 0000000..bfba06f
--- /dev/null
+++ b/pkgs/shared/src/types/index.ts
@@ -0,0 +1,79 @@
+// Card states for FSRS algorithm
+export const CardState = {
+	New: 0,
+	Learning: 1,
+	Review: 2,
+	Relearning: 3,
+} as const;
+
+export type CardState = (typeof CardState)[keyof typeof CardState];
+
+// Rating values for reviews
+export const Rating = {
+	Again: 1,
+	Hard: 2,
+	Good: 3,
+	Easy: 4,
+} as const;
+
+export type Rating = (typeof Rating)[keyof typeof Rating];
+
+// User
+export interface User {
+	id: string;
+	username: string;
+	passwordHash: string;
+	createdAt: Date;
+	updatedAt: Date;
+}
+
+// Deck
+export interface Deck {
+	id: string;
+	userId: string;
+	name: string;
+	description: string | null;
+	newCardsPerDay: number;
+	createdAt: Date;
+	updatedAt: Date;
+	deletedAt: Date | null;
+	syncVersion: number;
+}
+
+// Card with FSRS fields
+export interface Card {
+	id: string;
+	deckId: string;
+	front: string;
+	back: string;
+
+	// FSRS fields
+	state: CardState;
+	due: Date;
+	stability: number;
+	difficulty: number;
+	elapsedDays: number;
+	scheduledDays: number;
+	reps: number;
+	lapses: number;
+	lastReview: Date | null;
+
+	createdAt: Date;
+	updatedAt: Date;
+	deletedAt: Date | null;
+	syncVersion: number;
+}
+
+// ReviewLog (append-only)
+export interface ReviewLog {
+	id: string;
+	cardId: string;
+	userId: string;
+	rating: Rating;
+	state: CardState;
+	scheduledDays: number;
+	elapsedDays: number;
+	reviewedAt: Date;
+	durationMs: number | null;
+	syncVersion: number;
+}