fix: integer formatting, exploration durations, runestone preview, and gold achievement tracking

Closes #199
Closes #203
Closes #204
Closes #219
Closes #220
Closes #231
Closes #232

apps/api/src/routes/prestige.ts

@@ -15,6 +15,7 @@ import { updateChallengeProgress } from "../services/dailyChallenges.js";
 import { logger } from "../services/logger.js";
 import {
   buildPostPrestigeState,
+  calculatePrestigeThreshold,
   computeRunestoneMultipliers,
   isEligibleForPrestige,
 } from "../services/prestige.js";
@@ -40,10 +41,15 @@ prestigeRouter.post("/", async(context) => {
     const state = record.state as unknown as GameState;
 
     if (!isEligibleForPrestige(state)) {
+      const thresholdMultiplier
+        = state.transcendence?.echoPrestigeThresholdMultiplier ?? 1;
+      const required = calculatePrestigeThreshold(
+        state.prestige.count,
+        thresholdMultiplier,
+      );
       return context.json(
         {
-          // eslint-disable-next-line stylistic/max-len -- Error message cannot be shortened
-          error: "Not eligible for prestige — collect 1,000,000 total gold first",
+          error: `Not eligible for prestige — collect ${required.toLocaleString()} total gold first`,
         },
         400,
       );