feat: Phase 2 — game feel complete

Chemistry & squads:
- Chemistry calculation on GET /squad (club/league/nation links, max 100)
- Formation validation on POST /squad (exactly 11 starters, exactly 1 GK)

Objectives:
- Weekly objectives JSON (4 objectives: warrior, goals, dedicated, SBC)
- Daily objectives auto-reset at midnight UTC (background task)

SBC validation expanded:
- max_overall per-player enforcement
- required_clubs validation
- min_players_from_same_nation validation
- min_players_from_same_club validation

Market:
- GET /market?min_overall=X&position=Y filtering
- Expiry cleanup runs before every NPC refresh
- NPC market auto-refresh every 24h (background task, runs at startup)

Matches:
- GET /matches/opponent?difficulty=beginner|professional|world_class|legendary
  generates a random AI opponent squad from the card pool

Statistics:
- win_streak and best_win_streak tracking (migration 0002)
- GET /statistics/history?limit=N — last N matches with summary stats

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

src/routes/squad.rs

@@ -13,6 +13,7 @@ pub async fn get_squad(State(state): State<AppState>) -> AppResult<Json<Value>>
     let club = club_svc::get_club_by_profile(&state.pool, &profile.id).await?;
 
     let (squad, players) = squad_svc::get_squad(&state.pool, &club.id).await?;
+    let chemistry = squad_svc::calculate_chemistry(&state.pool, &state.card_db, &players).await?;
 
     let enriched: Vec<Value> = players
         .iter()
@@ -34,6 +35,7 @@ pub async fn get_squad(State(state): State<AppState>) -> AppResult<Json<Value>>
             "formation": squad.formation,
         },
         "players": enriched,
+        "chemistry": chemistry,
     })))
 }
 
@@ -44,6 +46,10 @@ pub async fn post_squad(
     let profile = profile_svc::get_active_profile(&state.pool).await?;
     let club = club_svc::get_club_by_profile(&state.pool, &profile.id).await?;
 
+    if !req.players.is_empty() {
+        squad_svc::validate_formation(&state.pool, &state.card_db, &req.players).await?;
+    }
+
     let squad = squad_svc::save_squad(&state.pool, &club.id, &req).await?;
     Ok(Json(json!({ "squad": squad })))
 }