feat: add equipment, achievements, and visual polish

- Equipment system: 12 items across weapon/armour/trinket slots with
  common/rare/epic/legendary rarities; starter commons auto-equipped,
  higher tiers drop from boss victories
- Achievement system: 15 milestones with typed conditions; checked
  each tick and crystal rewards applied automatically
- Achievement toast: slide-in notification, auto-dismisses after 4s
- Floating click text: +X gold floats on each manual click
- Expanded quests (9 total) and upgrades (12 total)
- Upgrade panel now shows locked upgrades so players can see their
  progression path
- formatNumber utility (K/M/B/T) used consistently across all panels
- Backfill logic for existing saves to add new content gracefully
- types package now emits .d.ts declarations

apps/api/prisma/schema.prisma

@@ -27,12 +27,3 @@ model GameState {
   updatedAt Float
 }
 
-model BossDamageLog {
-  id        String @id @default(auto()) @map("_id") @db.ObjectId
-  discordId String
-  bossId    String
-  damage    Float
-  dealtAt   Float
-
-  @@index([discordId, bossId, dealtAt])
-}