feat: content expansion, prestige shop, and offline earnings improvements

- Expand content to 18 zones, 72 bosses, 95 quests, 32 adventurer tiers
- Add prestige shop with 24 runestone upgrades across 5 categories
- Add PrestigeUpgrade type, data files, API routes, and frontend panel
- Fix offline earnings to include equipment and runestone multipliers
- Add offline essence calculation alongside offline gold
- Update OfflineModal to display both gold and essence earned
- Add IDEAS.md for tracking planned features

apps/web/src/context/GameContext.tsx

@@ -7,7 +7,12 @@ import {
   useRef,
   useState,
 } from "react";
-import { challengeBoss as challengeBossApi, loadGame, saveGame } from "../api/client.js";
+import {
+  buyPrestigeUpgrade as buyPrestigeUpgradeApi,
+  challengeBoss as challengeBossApi,
+  loadGame,
+  saveGame,
+} from "../api/client.js";
 import { RESOURCE_CAP, applyTick, calculateClickPower } from "../engine/tick.js";
 import { formatNumber as formatNumberUtil } from "../utils/format.js";
 
@@ -47,7 +52,9 @@ interface GameContextValue {
   syncError: string | null;
   /** Offline gold earned on login */
   offlineGold: number;
-  /** Dismiss the offline gold notification */
+  /** Offline essence earned on login */
+  offlineEssence: number;
+  /** Dismiss the offline earnings notification */
   dismissOfflineGold: () => void;
   /** Battle result to display in the modal (null when no battle pending) */
   battleResult: BattleResult | null;
@@ -63,6 +70,8 @@ interface GameContextValue {
   setNumberFormat: (format: NumberFormat) => void;
   /** Format a number using the player's chosen notation style */
   formatNumber: (value: number) => string;
+  /** Buy a prestige upgrade from the runestone shop */
+  buyPrestigeUpgrade: (upgradeId: string) => Promise<void>;
 }
 
 const GameContext = createContext<GameContextValue | null>(null);
@@ -74,6 +83,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
   const [isLoading, setIsLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
   const [offlineGold, setOfflineGold] = useState(0);
+  const [offlineEssence, setOfflineEssence] = useState(0);
   const [battleResult, setBattleResult] = useState<BattleResult | null>(null);
   const [newAchievements, setNewAchievements] = useState<Achievement[]>([]);
   const [lastSavedAt, setLastSavedAt] = useState<number | null>(null);
@@ -104,6 +114,9 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
       if (data.offlineGold > 0) {
         setOfflineGold(data.offlineGold);
       }
+      if (data.offlineEssence > 0) {
+        setOfflineEssence(data.offlineEssence);
+      }
       // Fetch number format preference from profile (fire-and-forget, non-blocking)
       void fetch(`/api/profile/${data.state.player.discordId}`)
         .then(async (res) => {
@@ -353,6 +366,29 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
     });
   }, []);
 
+  const buyPrestigeUpgrade = useCallback(async (upgradeId: string) => {
+    try {
+      const result = await buyPrestigeUpgradeApi({ upgradeId });
+      setState((prev) => {
+        if (!prev) return prev;
+        return {
+          ...prev,
+          prestige: {
+            ...prev.prestige,
+            runestones: result.runestonesRemaining,
+            purchasedUpgradeIds: result.purchasedUpgradeIds,
+            runestonesIncomeMultiplier: result.runestonesIncomeMultiplier,
+            runestonesClickMultiplier: result.runestonesClickMultiplier,
+            runestonesEssenceMultiplier: result.runestonesEssenceMultiplier,
+            runestonesCrystalMultiplier: result.runestonesCrystalMultiplier,
+          },
+        };
+      });
+    } catch {
+      // Silently ignore — server errors shouldn't crash the UI
+    }
+  }, []);
+
   const challengeBoss = useCallback(async (bossId: string) => {
     if (!stateRef.current) return;
     const boss = stateRef.current.bosses.find((b) => b.id === bossId);
@@ -464,6 +500,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
 
   const dismissOfflineGold = useCallback(() => {
     setOfflineGold(0);
+    setOfflineEssence(0);
   }, []);
 
   const dismissBattle = useCallback(() => {
@@ -498,6 +535,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
         forceSync,
         syncError,
         offlineGold,
+        offlineEssence,
         dismissOfflineGold,
         battleResult,
         dismissBattle,
@@ -506,6 +544,7 @@ export const GameProvider = ({ children }: { children: React.ReactNode }): React
         numberFormat,
         setNumberFormat,
         formatNumber: boundFormatNumber,
+        buyPrestigeUpgrade,
       }}
     >
       {children}