Main sections navigate to /admin (15 pages)
Detail/edit pages navigate to parent lists (16 pages)
All pages use useBackButton hook with proper navigation paths
Native Telegram back button in Mini App, UI button on web
Email template pages keep UI-only back buttons as required
- AdminPromocodes, AdminCampaigns, AdminPromoGroups, AdminTariffs, AdminServers
- Use flex-col on mobile, flex-row on desktop (sm:)
- Button now appears below header on small screens
- Prevents text wrapping in buttons
- Add AdminPromocodeCreate page for creating/editing promocodes
- Add AdminPromoGroups page for listing discount groups
- Add AdminPromoGroupCreate page for creating/editing discount groups
- Move promo groups from Promocodes section to separate admin section
- Simplify AdminPromocodes by removing embedded modals and groups tab
- Add routes and navigation for new pages
- Add i18n keys for all 4 locales (ru, en, zh, fa)
