fix: correct equipment balance and sort items by stat power (#69)

## Summary

Two improvements to the equipment system in one PR:

### Balance fixes (closes #54)

Full equipment audit revealed 9 items with duplicated stats, regressions, or purchasable items weaker than free boss drops:

| Item | Change | Reason |
|---|---|---|
| Void Conduit | 4x → 7x combat | 100M essence sink was equal to a zone-6 boss drop |
| Void Edge | 2.75x → 3.25x combat | Purchasable was weaker than free Celestial Blade (3x) |
| Astral Robe | 2.25x → 2.75x gold | Boss drop was weaker than purchasable Titan's Aegis (2.5x) |
| Philosopher's Stone | 2x → 2.25x click | Duplicated Frost Crystal's click multiplier |
| Eternal Flame | 1.15x → 1.25x gold | Gold regressed vs Philosopher's Stone (1.25x) |
| Celestial Focus | 2.5x → 3x click | 20M essence sink was weaker than free Angel's Halo (2.75x click + 1.3x gold) |
| Abyssal Tome | 3x → 3.75x gold | 50M essence sink was equal to free Heaven's Mantle (3x) |
| Crystal Matrix | 4x → 4.75x gold | 20M crystal sink was equal to free Sinslayer Aegis (4x) |
| Infernal Gem | 3.5x → 4x click | 5M crystal sink was identical to free Prism Eye |

### Equipment sorting (closes #55)

Equipment cards within each slot now render in ascending order of combined bonus power — the sum of all multiplier bonuses — so stronger items always appear further down the list. Hybrid items such as Volcanic Plate sort correctly without needing a per-slot primary stat.

## Test plan

- [ ] All purchasable weapons/armour/trinkets now exceed the stats of the highest free boss drop at their tier
- [ ] No duplicate stat values between adjacent items in the same progression track
- [ ] Equipment cards within each slot render weakest → strongest
- [ ] Hybrid multi-stat items sort sensibly alongside single-stat items
- [ ] Full pipeline green (lint + build + tests at 100% coverage)

✨ This PR was created with help from Hikari~ 🌸

Reviewed-on: #69
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/api/src/data/equipment.ts

@@ -101,7 +101,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "weapon",
   },
   {
-    bonus: { combatMultiplier: 2.75 },
+    bonus: { combatMultiplier: 3.25 },
     cost:  { crystals: 500, essence: 2000, gold: 0 },
     description:
       "A blade made of compressed nothingness. It does not cut — it simply unmakes.",
@@ -204,7 +204,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "armour",
   },
   {
-    bonus: { goldMultiplier: 2.25 },
+    bonus: { goldMultiplier: 2.75 },
     description:
       "Woven from threads of pure starlight harvested by the Astral Wraith. Income flows like cosmic energy.",
     equipped: false,
@@ -305,7 +305,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "trinket",
   },
   {
-    bonus: { clickMultiplier: 2, goldMultiplier: 1.25 },
+    bonus: { clickMultiplier: 2.25, goldMultiplier: 1.25 },
     description:
       "The legendary stone that grants mastery over gold and combat alike.",
     equipped: false,
@@ -316,7 +316,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "trinket",
   },
   {
-    bonus: { clickMultiplier: 2.25, goldMultiplier: 1.15 },
+    bonus: { clickMultiplier: 2.25, goldMultiplier: 1.25 },
     description:
       "A flame that has never been extinguished, sealed in crystal by the Phoenix Lord. It burns with the power of rebirth.",
     equipped: false,
@@ -697,7 +697,7 @@ export const defaultEquipment: Array<Equipment> = [
   },
   // ── Purchasable endgame sinks ─────────────────────────────────────────────
   {
-    bonus: { clickMultiplier: 2.5 },
+    bonus: { clickMultiplier: 3 },
     cost:  { crystals: 0, essence: 20_000_000, gold: 0 },
     description:
       "A lens of compressed celestial light that sharpens every strike with divine precision.",
@@ -709,7 +709,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "trinket",
   },
   {
-    bonus: { goldMultiplier: 3 },
+    bonus: { goldMultiplier: 3.75 },
     cost:  { crystals: 0, essence: 50_000_000, gold: 0 },
     description:
       "A book written in the language of the deep — reading it aligns your guild's operations with abyssal efficiency.",
@@ -721,7 +721,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "armour",
   },
   {
-    bonus: { combatMultiplier: 4 },
+    bonus: { combatMultiplier: 7 },
     cost:  { crystals: 0, essence: 100_000_000, gold: 0 },
     description:
       "A weapon that channels void energy — the absence of resistance makes every strike devastating.",
@@ -733,7 +733,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "weapon",
   },
   {
-    bonus: { clickMultiplier: 3.5, goldMultiplier: 1.5 },
+    bonus: { clickMultiplier: 4, goldMultiplier: 1.5 },
     cost:  { crystals: 5_000_000, essence: 0, gold: 0 },
     description:
       "A gem forged in the heart of the Infernal Court — it burns with productivity and righteous fury in equal measure.",
@@ -745,7 +745,7 @@ export const defaultEquipment: Array<Equipment> = [
     type:     "trinket",
   },
   {
-    bonus: { goldMultiplier: 4 },
+    bonus: { goldMultiplier: 4.75 },
     cost:  { crystals: 20_000_000, essence: 0, gold: 0 },
     description:
       "Armour structured around a crystalline lattice of optimal income calculations. Every gold piece finds you faster.",