Phase 10: card upgrade system (chemistry styles, position change, training)

- GET /chemistry-styles — lists 18 FUT-style chemistry styles with stat boost breakdowns
- POST /collection/:id/chemistry-style — apply a style (Shadow, Hunter, Anchor, etc.)
- POST /collection/:id/position — override a player's position for 500 coins
- POST /collection/:id/training — add +1/+2/+3 OVR training bonus (max +3 total)
- GET /collection now includes chemistry_style, position_override, training_bonus,
  effective_overall and effective_position fields per owned card
- Migration 0007 adds three columns to owned_cards with safe defaults
- 10 new integration tests — all 55 pass, clippy clean

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

src/routes/mod.rs

@@ -15,3 +15,4 @@ pub mod sbc;
 pub mod settings;
 pub mod squad;
 pub mod statistics;
+pub mod upgrades;