UI improvements: filters, map layout, search bar

- Add hubCountries query and country filter for hubs page
- Add getAvailableProducts query for offers (only products with active offers)
- Add sourceLatitude/sourceLongitude to orders GraphQL
- Fix ListMapLayout with position fixed for proper map height
- GlobalSearchBar: make fields wider, remove unit selector
- Remove status/isVerified filters from suppliers/offers (backend handles this)

graphql/operations/public/exchange/GetAvailableProducts.graphql

@@ -0,0 +1,9 @@
+query GetAvailableProducts {
+  getAvailableProducts {
+    uuid
+    name
+    categoryId
+    categoryName
+    terminusSchemaId
+  }
+}