Phase 11: FUT Champions mode and Division Rivals weekly rewards

FUT Champions (Weekend League):
- POST /fut-champs/start — open a new 30-match week (one active session at a time)
- GET /fut-champs — current session status with matches_remaining
- POST /fut-champs/:id/result — record a match; auto-completes and computes tier at 30
- POST /fut-champs/:id/claim — claim coins + pack reward (idempotent guard)
- GET /fut-champs/history — past sessions newest-first
- 11 reward tiers: Elite (27+ wins, 50k coins + icon pack) down to Bronze 1 (0 wins, 250 coins)

Division Rivals:
- POST /rivals/claim-weekly — claim weekly reward scaled by current division
- Week counter is monotonic (offline-safe, no real-time calendar dependency)
- Division 1-3 get a bonus pack alongside coins

Migration 0008 adds fut_champs_sessions table and two columns to seasons.
12 new integration tests — all 67 pass, clippy clean.

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

src/models/mod.rs

@@ -2,6 +2,7 @@ pub mod card;
 pub mod chemistry_style;
 pub mod club;
 pub mod draft;
+pub mod fut_champs;
 pub mod event;
 pub mod season;
 pub mod market;