feat: add CSV/JSON export, advanced bulk filters & selection to Catalog Manager

- Admin Audit Log: CSV/JSON export via ?format=query param
- Catalog Manager: club_only / have_offer filters (multi-filter support)
- Offer discovery: refactored discoverOffers() to accept filters object
- Translations added for new filter labels
- Test updates for all modified paths

src/messages/en.json

@@ -2331,12 +2331,18 @@
 				"discovery": {
 					"searchPlaceholder": "Name, classname, furniture ID or #offer ID…",
 					"filterLabel": "Filter offers",
+					"clubOnlyFilterLabel": "HC Only Filter",
+					"haveOfferFilterLabel": "Has Offer Filter",
 					"filters": {
 						"all": "All offers",
 						"free": "Free",
 						"paid": "Paid",
 						"bundles": "Bundles",
-						"limited": "Limited editions"
+						"limited": "Limited editions",
+						"club_only_yes": "HC Only",
+						"club_only_no": "Not HC Only",
+						"have_offer_yes": "Has Offer",
+						"have_offer_no": "No Offer"
 					},
 					"shown": "({count} shown)",
 					"selected": "{count} selected",