Phase 9: division/season tracking, club customization, pack history, notifications

- GET /division returns live season stats (points, record, promotion threshold)
- PUT /club allows updating club name and manager_name
- GET /packs/history returns opened packs with full card definitions
- GET /notifications dynamically surfaces completed objectives, expiring loans, season end
- Club model gains manager_name column (migration 0006 already added it)
- Pack model gains opened_cards and opened_at; pack SELECT queries updated
- 9 new integration tests — all 45 pass, clippy clean

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

src/models/club.rs

@@ -11,6 +11,7 @@ pub struct Club {
     pub level: i64,
     pub created_at: DateTime<Utc>,
     pub updated_at: DateTime<Utc>,
+    pub manager_name: Option<String>,
 }
 
 impl Club {
@@ -24,6 +25,7 @@ impl Club {
             level: 1,
             created_at: now,
             updated_at: now,
+            manager_name: Some("Player Manager".to_string()),
         }
     }
 }