feat: partner-campaign integration in admin UI

- Add partner badge to campaigns list
- Add partner selector dropdown in campaign edit
- Support ?partnerId= query param in campaign create (replaces separate page)
- Filter already-assigned campaigns in partner assign flow
- Show taken campaigns greyed out with partner name
- Delete AdminPartnerCampaignCreate (replaced by query param approach)
- Add partner translations (ru, en, zh, fa)

src/pages/AdminPartnerDetail.tsx

@@ -216,7 +216,7 @@ export default function AdminPartnerDetail() {
                 {t('admin.partnerDetail.campaigns.assign')}
               </button>
               <button
-                onClick={() => navigate(`/admin/partners/${userId}/campaigns/create`)}
+                onClick={() => navigate(`/admin/campaigns/create?partnerId=${userId}`)}
                 className="rounded-lg bg-accent-500/20 px-3 py-1.5 text-xs font-medium text-accent-400 transition-colors hover:bg-accent-500/30"
               >
                 {t('admin.partnerDetail.campaigns.createNew')}