feat: major content expansion with essence and crystal sinks

- 6 zones (up from 3): Shadow Marshes, Volcanic Depths, Astral Void
- 18 bosses (up from 4): 3 per zone with zone-based sequential unlock
- 24 quests (up from 9): 3-4 per zone, reorganised by zone
- 15 adventurer tiers (up from 10): Shadow Assassin through Divine Champion
- 28 equipment pieces (up from 12): boss drops + purchasable with essence/crystals
- 24 upgrades (up from 13): crystal-cost upgrades + new adventurer upgrades
- 22 achievements (up from 14): new milestones for bosses, quests, gold, armies
- Purchasable equipment system: buy items directly with essence or crystals
- Crystal-cost upgrades: spend crystals on global and click power boosts
- Zone-based boss progression: defeating a zone's last boss unlocks the next zone

apps/web/src/context/GameContext.tsx

@@ -25,6 +25,8 @@ interface GameContextValue {
   buyAdventurer: (adventurerId: string) => void;
   /** Buy an upgrade */
   buyUpgrade: (upgradeId: string) => void;
+  /** Purchase a buyable equipment item */
+  buyEquipment: (equipmentId: string) => void;
   /** Start a quest */
   startQuest: (questId: string) => void;
   /** Challenge a boss — runs full server-side simulation */
@@ -175,6 +177,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
       if (!upgrade || !upgrade.unlocked || upgrade.purchased) return prev;
       if (prev.resources.gold < upgrade.costGold) return prev;
       if (prev.resources.essence < upgrade.costEssence) return prev;
+      if (prev.resources.crystals < (upgrade.costCrystals ?? 0)) return prev;
 
       return {
         ...prev,
@@ -182,6 +185,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
           ...prev.resources,
           gold: prev.resources.gold - upgrade.costGold,
           essence: prev.resources.essence - upgrade.costEssence,
+          crystals: prev.resources.crystals - (upgrade.costCrystals ?? 0),
         },
         upgrades: prev.upgrades.map((u) =>
           u.id === upgradeId ? { ...u, purchased: true } : u,
@@ -225,6 +229,37 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
     });
   }, []);
 
+  const buyEquipment = useCallback((equipmentId: string) => {
+    setState((prev) => {
+      if (!prev) return prev;
+      const item = (prev.equipment ?? []).find((e) => e.id === equipmentId);
+      if (!item || item.owned || !item.cost) return prev;
+
+      const { gold, essence, crystals } = item.cost;
+      if (prev.resources.gold < gold) return prev;
+      if (prev.resources.essence < essence) return prev;
+      if (prev.resources.crystals < crystals) return prev;
+
+      const slotAlreadyEquipped = (prev.equipment ?? []).some(
+        (e) => e.type === item.type && e.equipped,
+      );
+
+      return {
+        ...prev,
+        resources: {
+          ...prev.resources,
+          gold: prev.resources.gold - gold,
+          essence: prev.resources.essence - essence,
+          crystals: prev.resources.crystals - crystals,
+        },
+        equipment: (prev.equipment ?? []).map((e) => {
+          if (e.id === equipmentId) return { ...e, owned: true, equipped: !slotAlreadyEquipped };
+          return e;
+        }),
+      };
+    });
+  }, []);
+
   const challengeBoss = useCallback(async (bossId: string) => {
     if (!stateRef.current) return;
     const boss = stateRef.current.bosses.find((b) => b.id === bossId);
@@ -238,21 +273,33 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
         if (!prev) return prev;
 
         if (result.won) {
-          const bossIndex = prev.bosses.findIndex((b) => b.id === bossId);
+          const defeatedBoss = prev.bosses.find((b) => b.id === bossId);
+          const zoneBosses = prev.bosses.filter((b) => b.zoneId === defeatedBoss?.zoneId);
+          const zoneIdx = zoneBosses.findIndex((b) => b.id === bossId);
+          const nextZoneBossId = zoneBosses[zoneIdx + 1]?.id;
+
+          // Find newly unlocked zones and their first bosses
+          const newlyUnlockedZones = (prev.zones ?? []).filter((z) => z.unlockBossId === bossId && z.status === "locked");
+          const newZoneFirstBossIds = newlyUnlockedZones.map((z) => {
+            const firstBoss = prev.bosses.find((b) => b.zoneId === z.id);
+            return firstBoss?.id;
+          }).filter(Boolean);
+
           return {
             ...prev,
-            bosses: prev.bosses.map((b, idx) => {
-              if (b.id === bossId) {
-                return { ...b, status: "defeated" as const, currentHp: 0 };
+            bosses: prev.bosses.map((b) => {
+              if (b.id === bossId) return { ...b, status: "defeated" as const, currentHp: 0 };
+              if (b.id === nextZoneBossId && b.prestigeRequirement <= prev.prestige.count) {
+                return { ...b, status: "available" as const };
               }
-              if (
-                idx === bossIndex + 1 &&
-                b.prestigeRequirement <= prev.prestige.count
-              ) {
+              if (newZoneFirstBossIds.includes(b.id) && b.prestigeRequirement <= prev.prestige.count) {
                 return { ...b, status: "available" as const };
               }
               return b;
             }),
+            zones: (prev.zones ?? []).map((z) =>
+              z.unlockBossId === bossId ? { ...z, status: "unlocked" as const } : z,
+            ),
             resources: result.rewards
               ? {
                   ...prev.resources,
@@ -332,6 +379,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
         handleClick,
         buyAdventurer,
         buyUpgrade,
+        buyEquipment,
         startQuest,
         challengeBoss,
         equipItem,