feat(server): add card CRUD endpoints

Implement card management API with create, read, update, and delete
operations. Cards are nested under decks (/api/decks/:deckId/cards)
with deck ownership verification on all operations.

- Add Card interface and CardRepository to repository types
- Create cardRepository with CRUD operations and soft delete
- Add card routes with Zod validation and auth middleware
- Include 29 tests covering all endpoints and error cases

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

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

1 files changed, 1 insertions, 0 deletions

diff --git a/src/server/routes/index.ts b/src/server/routes/index.ts
index 43a3a07..009f2c3 100644
--- a/src/server/routes/index.ts
+++ b/src/server/routes/index.ts
@@ -1,2 +1,3 @@
 export { auth } from "./auth.js";
+export { cards } from "./cards.js";
 export { decks } from "./decks.js";