chore: remove dead code, unused CSS, unused components, and clean up git tracking

- Remove storage/logs/ and prod.log from git tracking; add to .gitignore
- Remove unused AvatarCarousel and ArticleSlider components
- Remove unused SkeletonTable export from ui.tsx
- Remove unused ChevronDown import from admin layout
- Remove 13 unused CSS classes (icon-base, nav-*, navigation-icon*, .app.dark,
  text-body, transition-base, card-base, admin-info-grid, .coin.*)
- Remove duplicate translation keys (openMenu/closeMenu in en.json)
- Fix admin-bans to use Prisma-generated bans_type enum
- Create shared AdminPageHeader component and formatDate utility
- Add logger and generateRequestId for structured logging
- All 58 tests pass, typecheck clean, build succeeds

src/app/admin/layout.tsx

@@ -11,7 +11,7 @@ import {
   Store, ShoppingCart, Receipt, Ticket, CreditCard, Gem, Award, Trophy, Calendar,
   Radio, History,
   Terminal, Monitor, Bell, FileText, Filter, Wrench, Settings, DoorOpen, Mail, Palette, Cog,
-  ChevronDown, LogOut,
+  LogOut,
 } from "lucide-react";
 
 export const dynamic = "force-dynamic";