wip(fifa17): pre-existing SBC/economy candidate snapshot

Snapshot of the uncommitted economy/SBC candidate work that built the tested
sbc-host on top of e8d1c1d (NOT authored in this session; committed to leave a
clean tree). Covers pack_content, sbc, store_catalog, host economy_store/lib,
purchasegroup fixtures, economy integration/concurrency/differential tests,
and Cargo.lock. Content matches the running staging host binary.

openfut-utas-host/tests/economy_concurrency.rs

@@ -311,7 +311,7 @@ fn case_a_two_buys(h: &Harness) -> String {
             refs, 1,
             "exactly one BUY refused 461 (statuses {statuses:?})"
         );
-        // The winner minted 5 cards; the loser minted nothing.
+        // The winner minted 12 cards (real Bronze Pack); the loser minted nothing.
         for r in &rs {
             if r.status == 200 {
                 assert_eq!(
@@ -319,7 +319,7 @@ fn case_a_two_buys(h: &Harness) -> String {
                         .as_array()
                         .unwrap()
                         .len(),
-                    5
+                    12
                 );
             }
         }