feat(economy): purchase_items primitive + entitlement import seeding

purchase_items: generic atomic debit + mint of several items (fail-closed) for
open-on-buy Store packs (Store BUY returns items immediately) + POST
/economy/purchase-items route. Import: add optional entitlements[] to
ProfileImportRequest, seeding unconsumed packs rows in the same transaction (so a
source's unopened packs become Core entitlements); idempotency via the existing
import fingerprint. Tests: 2 purchase_items unit + endpoint + entitlement-seed
import. Core matrix 45 lib + 116 integration + 9 import green; clippy clean.

src/routes/economy.rs

@@ -144,3 +144,20 @@ pub async fn post_purchase_item(
         economy::purchase_item(&state.pool, &club, req.cost, &req.item_id, &req.card_id).await?;
     Ok(Json(BalanceResponse { balance }))
 }
+
+#[derive(Deserialize)]
+pub struct PurchaseItemsRequest {
+    pub cost: i64,
+    pub items: Vec<GrantedItem>,
+}
+
+/// `POST /economy/purchase-items` — atomic debit + mint several items.
+pub async fn post_purchase_items(
+    State(state): State<AppState>,
+    game: GameId,
+    Json(req): Json<PurchaseItemsRequest>,
+) -> AppResult<Json<BalanceResponse>> {
+    let club = resolve_club(&state, &game).await?;
+    let balance = economy::purchase_items(&state.pool, &club, req.cost, &req.items).await?;
+    Ok(Json(BalanceResponse { balance }))
+}