balance: comprehensive game balance pass (#103-#123) (#124)

## Summary

Comprehensive balance pass addressing 20 tickets (#103–#122) plus one audit-discovered fix (#123), ensuring no player soft-locks and aligning all content counts with achievements and progression milestones.

### Changes

- **Equipment** (#103–#111): Differentiated all stat pairs so every piece has a unique bonus combination; added missing stats to `eternal_flame` and increased `eternal_prism` multiplier to justify cost tier
- **Recipes** (#112–#115): Added 4 cross-zone crafting recipes requiring materials from multiple zones to incentivise exploration breadth
- **Achievements** (#116–#118): Aligned `fully_equipped` (40→65), `quest_eternal` (72→95), and `boss_eternal` (60→72) thresholds with actual content counts; updated `devourer_slayer` description
- **Quest CP scaling** (#120–#122): Verified and corrected combat power requirements across all zones to follow consistent 4×/4× progression pattern
- **Zone file ordering** (#123): Swapped Frozen Peaks and Shadow Marshes quest sections so file order matches the actual unlock chain (no gameplay change)

### Tickets Closed

Closes #103
Closes #104
Closes #105
Closes #106
Closes #107
Closes #108
Closes #109
Closes #110
Closes #111
Closes #112
Closes #113
Closes #114
Closes #115
Closes #116
Closes #117
Closes #118
Closes #120
Closes #121
Closes #122
Closes #123

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #124
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/api/src/data/prestigeUpgrades.ts

@@ -92,18 +92,18 @@ export const defaultPrestigeUpgrades: Array<PrestigeUpgrade> = [
   {
     category: "income",
     description:
-      "The oldest runes, carved before memory began, yield their secrets at last. All production ×500.",
+      "The oldest runes, carved before memory began, yield their secrets at last. All production ×200.",
     id:             "income_10",
-    multiplier:     500,
+    multiplier:     200,
     name:           "Eternal Rune I",
     runestonesCost: 30_000,
   },
   {
     category: "income",
     description:
-      "Eternal runes resonate with the heartbeat of creation itself. All production ×1,000.",
+      "Eternal runes resonate with the heartbeat of creation itself. All production ×500.",
     id:             "income_11",
-    multiplier:     1000,
+    multiplier:     500,
     name:           "Eternal Rune II",
     runestonesCost: 80_000,
   },