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/src/data/equipment.ts

@@ -0,0 +1,127 @@
+import type { Equipment } from "@elysium/types";
+
+export const DEFAULT_EQUIPMENT: Equipment[] = [
+  // Weapons — drop from bosses; common starts owned
+  {
+    id: "rusty_sword",
+    name: "Rusty Sword",
+    description: "A battered blade, but still sharp enough to draw blood.",
+    type: "weapon",
+    rarity: "common",
+    bonus: { combatMultiplier: 1.1 },
+    owned: true,
+    equipped: true,
+  },
+  {
+    id: "iron_sword",
+    name: "Iron Sword",
+    description: "A sturdy weapon issued to veterans of the guild.",
+    type: "weapon",
+    rarity: "rare",
+    bonus: { combatMultiplier: 1.25 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "enchanted_blade",
+    name: "Enchanted Blade",
+    description: "A sword imbued with ancient magic that makes every strike count.",
+    type: "weapon",
+    rarity: "epic",
+    bonus: { combatMultiplier: 1.5 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "vorpal_sword",
+    name: "Vorpal Sword",
+    description: "A legendary blade that severs even the strongest bonds.",
+    type: "weapon",
+    rarity: "legendary",
+    bonus: { combatMultiplier: 2.0 },
+    owned: false,
+    equipped: false,
+  },
+  // Armour — drop from bosses; common starts owned
+  {
+    id: "leather_armour",
+    name: "Leather Armour",
+    description: "Simple protection that keeps your adventurers moving efficiently.",
+    type: "armour",
+    rarity: "common",
+    bonus: { goldMultiplier: 1.1 },
+    owned: true,
+    equipped: true,
+  },
+  {
+    id: "chainmail",
+    name: "Chainmail",
+    description: "Interlocked rings that guard against most mundane threats.",
+    type: "armour",
+    rarity: "rare",
+    bonus: { goldMultiplier: 1.25 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "plate_armour",
+    name: "Plate Armour",
+    description: "Full plate protection that inspires confidence — and gold.",
+    type: "armour",
+    rarity: "epic",
+    bonus: { goldMultiplier: 1.5 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "dragon_scale",
+    name: "Dragon Scale Armour",
+    description: "Armour forged from the scales of a defeated elder dragon.",
+    type: "armour",
+    rarity: "legendary",
+    bonus: { goldMultiplier: 2.0 },
+    owned: false,
+    equipped: false,
+  },
+  // Trinkets — drop from bosses; common starts owned
+  {
+    id: "lucky_coin",
+    name: "Lucky Coin",
+    description: "A coin that always lands on the side you need.",
+    type: "trinket",
+    rarity: "common",
+    bonus: { clickMultiplier: 1.1 },
+    owned: true,
+    equipped: true,
+  },
+  {
+    id: "mages_focus",
+    name: "Mage's Focus",
+    description: "A crystal lens that sharpens magical precision.",
+    type: "trinket",
+    rarity: "rare",
+    bonus: { clickMultiplier: 1.25 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "arcane_orb",
+    name: "Arcane Orb",
+    description: "An orb humming with concentrated arcane energy.",
+    type: "trinket",
+    rarity: "epic",
+    bonus: { clickMultiplier: 1.5 },
+    owned: false,
+    equipped: false,
+  },
+  {
+    id: "philosophers_stone",
+    name: "Philosopher's Stone",
+    description: "The legendary stone that grants mastery over gold and combat alike.",
+    type: "trinket",
+    rarity: "legendary",
+    bonus: { clickMultiplier: 2.0, goldMultiplier: 1.25 },
+    owned: false,
+    equipped: false,
+  },
+];