fifa17 store: native category art via displayGroupAssetId

The all-groups landing (shown on first store entry) renders one tile per group
whose background is the client-bundled packs_backgrounds_%d.dds, selected by
displayGroupAssetId. Live-probed on the retail client 2026-08-18: index 0 is
blank; indices 1/2/3 render real pack art. Assign non-zero per category
(bronze=1, silver=2, gold/mypacks=3) so that landing shows native pack art
instead of blank shields. The persistent tabbed store (MY PACKS/BRONZE/SILVER/
GOLD PACKS) draws pack art from the packs themselves and is unaffected.

LIVE-CONFIRMED end-to-end: native tabbed store renders the real 6-pack catalogue
with correct prices (Gold 5000 / Premium Gold 7500), counts (12 items, 10 gold,
1/3 rares), pack art, and no "or %1s" line.

openfut-adapter-fifa17/tests/fixtures/purchasegroup_zero_clean.json

@@ -13,6 +13,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 1,
+      "displayGroupAssetId": 1,
       "currencies": [
         {
           "name": "coins",
@@ -45,6 +46,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 2,
+      "displayGroupAssetId": 1,
       "currencies": [
         {
           "name": "coins",
@@ -77,6 +79,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 3,
+      "displayGroupAssetId": 2,
       "currencies": [
         {
           "name": "coins",
@@ -109,6 +112,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 4,
+      "displayGroupAssetId": 2,
       "currencies": [
         {
           "name": "coins",
@@ -141,6 +145,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 5,
+      "displayGroupAssetId": 3,
       "currencies": [
         {
           "name": "coins",
@@ -173,6 +178,7 @@
       "purchaseCount": 0,
       "isPremium": false,
       "sortPriority": 6,
+      "displayGroupAssetId": 3,
       "currencies": [
         {
           "name": "coins",