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/achievements.ts

@@ -0,0 +1,139 @@
+import type { Achievement } from "@elysium/types";
+
+export const DEFAULT_ACHIEVEMENTS: Achievement[] = [
+  {
+    id: "first_click",
+    name: "First Strike",
+    description: "Click the Guild Hall for the first time.",
+    icon: "👆",
+    condition: { type: "totalClicks", amount: 1 },
+    reward: { crystals: 5 },
+    unlockedAt: null,
+  },
+  {
+    id: "click_enthusiast",
+    name: "Click Enthusiast",
+    description: "Click the Guild Hall 100 times.",
+    icon: "🖱️",
+    condition: { type: "totalClicks", amount: 100 },
+    reward: { crystals: 25 },
+    unlockedAt: null,
+  },
+  {
+    id: "click_master",
+    name: "Click Master",
+    description: "Click the Guild Hall 1,000 times.",
+    icon: "⚡",
+    condition: { type: "totalClicks", amount: 1_000 },
+    reward: { crystals: 100 },
+    unlockedAt: null,
+  },
+  {
+    id: "first_gold",
+    name: "First Gold",
+    description: "Earn your first 100 gold.",
+    icon: "🪙",
+    condition: { type: "totalGoldEarned", amount: 100 },
+    reward: { crystals: 5 },
+    unlockedAt: null,
+  },
+  {
+    id: "wealthy",
+    name: "Wealthy",
+    description: "Earn 10,000 gold in total.",
+    icon: "💰",
+    condition: { type: "totalGoldEarned", amount: 10_000 },
+    reward: { crystals: 25 },
+    unlockedAt: null,
+  },
+  {
+    id: "rich",
+    name: "Rich",
+    description: "Earn 1,000,000 gold in total.",
+    icon: "👑",
+    condition: { type: "totalGoldEarned", amount: 1_000_000 },
+    reward: { crystals: 100 },
+    unlockedAt: null,
+  },
+  {
+    id: "billionaire",
+    name: "Billionaire",
+    description: "Earn 1,000,000,000 gold in total.",
+    icon: "🏦",
+    condition: { type: "totalGoldEarned", amount: 1_000_000_000 },
+    reward: { crystals: 500 },
+    unlockedAt: null,
+  },
+  {
+    id: "first_quest",
+    name: "Adventurous Spirit",
+    description: "Complete your first quest.",
+    icon: "📜",
+    condition: { type: "questsCompleted", amount: 1 },
+    reward: { crystals: 10 },
+    unlockedAt: null,
+  },
+  {
+    id: "quest_veteran",
+    name: "Quest Veteran",
+    description: "Complete 5 quests.",
+    icon: "📚",
+    condition: { type: "questsCompleted", amount: 5 },
+    reward: { crystals: 50 },
+    unlockedAt: null,
+  },
+  {
+    id: "boss_slayer",
+    name: "Boss Slayer",
+    description: "Defeat your first boss.",
+    icon: "⚔️",
+    condition: { type: "bossesDefeated", amount: 1 },
+    reward: { crystals: 25 },
+    unlockedAt: null,
+  },
+  {
+    id: "legendary_hunter",
+    name: "Legendary Hunter",
+    description: "Defeat all four bosses.",
+    icon: "🏆",
+    condition: { type: "bossesDefeated", amount: 4 },
+    reward: { crystals: 200 },
+    unlockedAt: null,
+  },
+  {
+    id: "guild_master",
+    name: "Guild Master",
+    description: "Recruit a total of 50 adventurers.",
+    icon: "🏰",
+    condition: { type: "adventurerTotal", amount: 50 },
+    reward: { crystals: 50 },
+    unlockedAt: null,
+  },
+  {
+    id: "army_commander",
+    name: "Army Commander",
+    description: "Recruit a total of 500 adventurers.",
+    icon: "🛡️",
+    condition: { type: "adventurerTotal", amount: 500 },
+    reward: { crystals: 200 },
+    unlockedAt: null,
+  },
+  {
+    id: "first_prestige",
+    name: "Born Again",
+    description: "Prestige for the first time.",
+    icon: "⭐",
+    condition: { type: "prestigeCount", amount: 1 },
+    reward: { crystals: 100 },
+    unlockedAt: null,
+  },
+  {
+    id: "collector",
+    name: "Collector",
+    description: "Acquire your first piece of boss-dropped equipment.",
+    icon: "🎒",
+    condition: { type: "equipmentOwned", amount: 4 },
+    reward: { crystals: 10 },
+    unlockedAt: null,
+  },
+];