Phase 24: daily check-in system + club milestones endpoint

- migrations/0012_daily_checkin.sql: daily_checkins table tracking streak,
  coins awarded, pack granted, timestamp per profile
- services/checkin.rs: get_status() (available, streak_day, next reward),
  claim() (idempotent same-day guard, streak logic: continue if yesterday
  or today, else reset; 7-day cycle with STREAK_COINS array, day-7 pack)
- routes/club.rs: GET /club/checkin, POST /club/checkin, GET /club/milestones
  (computed from statistics, season_history, owned_cards, sbc_submissions,
  daily_checkins tables; no new DB tables needed)
- 4 new integration tests: checkin available initially, claim awards coins,
  idempotent same-day, milestones endpoint structure (93 → 93+4=97 tests)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app.rs

@@ -135,6 +135,9 @@ pub async fn build(pool: Pool, cfg: Config) -> Result<Router> {
         .route("/profile", get(routes::profile::get_profile))
         .route("/club", get(routes::club::get_club))
         .route("/club", put(routes::club::put_club))
+        .route("/club/checkin", get(routes::club::get_checkin_status))
+        .route("/club/checkin", post(routes::club::post_checkin))
+        .route("/club/milestones", get(routes::club::get_milestones))
         .route("/cards", get(routes::cards::get_cards))
         .route("/cards/:card_id", get(routes::cards::get_card))
         .route("/collection", get(routes::cards::get_collection))