balance: cap quest failure rates at 15% (closes #172)

Proportionally scaled all zoneFailureChance values from the old
4%-40% range down to 4%-15%, preserving the relative gradient
across zones. A 7-hour quest failing 40% of the time was too
punishing; 15% max keeps risk meaningful without being cruel.

Closes #172

apps/web/src/engine/tick.ts

@@ -95,29 +95,29 @@ export const PRESTIGE_COMBAT_BASE = 4;
 export const RESOURCE_CAP = 1e300;
 
 /**
- * Probability of quest failure per zone — scales from 10% (early game) to 40% (end game).
+ * Probability of quest failure per zone — scales from 4% (early game) to 15% (end game).
  * On failure the quest resets to "available" with no rewards; the player must wait the
  * full duration again on their next attempt.
  */
 export const zoneFailureChance: Record<string, number> = {
-  abyssal_trench:    0.24,
-  astral_void:       0.2,
-  celestial_reaches: 0.22,
-  cosmic_maelstrom:  0.4,
-  crystalline_spire: 0.28,
-  eternal_throne:    0.32,
-  frozen_peaks:      0.14,
-  infernal_court:    0.26,
-  infinite_expanse:  0.36,
-  primeval_sanctum:  0.4,
-  primordial_chaos:  0.34,
-  reality_forge:     0.38,
-  shadow_marshes:    0.16,
-  shattered_ruins:   0.12,
-  the_absolute:      0.4,
-  verdant_vale:      0.1,
-  void_sanctum:      0.3,
-  volcanic_depths:   0.18,
+  abyssal_trench:    0.09,
+  astral_void:       0.08,
+  celestial_reaches: 0.08,
+  cosmic_maelstrom:  0.15,
+  crystalline_spire: 0.11,
+  eternal_throne:    0.12,
+  frozen_peaks:      0.05,
+  infernal_court:    0.1,
+  infinite_expanse:  0.14,
+  primeval_sanctum:  0.15,
+  primordial_chaos:  0.13,
+  reality_forge:     0.14,
+  shadow_marshes:    0.06,
+  shattered_ruins:   0.05,
+  the_absolute:      0.15,
+  verdant_vale:      0.04,
+  void_sanctum:      0.11,
+  volcanic_depths:   0.07,
 };
 
 /**