fix: break fire_temple combat power wall (#96)

Closes #95

## Summary

`void_walker` adventurers (130K combat power each) were locked behind `fire_temple`, which requires 4.8B combat power. The best adventurer available before completing that quest was `arcane_scholar` at 45K CP each — meaning players needed ~107K arcane scholars to break through, versus ~37K if they had void walkers. Classic chicken-and-egg wall.

## Changes

- Moved `void_walker` adventurer reward from `fire_temple` to `lava_flows` (the entry quest to Volcanic Depths, no CP requirement)
- Added 40M gold reward to `fire_temple` to replace the removed adventurer unlock

Players now unlock `void_walker` as soon as they enter the zone, giving them the combat power boost before they need to grind toward the temple.

✨ This issue was created with help from Hikari~ 🌸

Reviewed-on: #96
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/api/src/data/quests.ts

@@ -264,6 +264,7 @@ export const defaultQuests: Array<Quest> = [
     rewards:         [
       { amount: 15_000_000, type: "gold" },
       { amount: 4000, type: "essence" },
+      { targetId: "void_walker", type: "adventurer" },
     ],
     status: "locked",
     zoneId: "volcanic_depths",
@@ -277,9 +278,9 @@ export const defaultQuests: Array<Quest> = [
     name:            "The Temple of the Flame",
     prerequisiteIds: [ "lava_flows" ],
     rewards:         [
+      { amount: 40_000_000, type: "gold" },
       { amount: 12_000, type: "essence" },
       { amount: 300, type: "crystals" },
-      { targetId: "void_walker", type: "adventurer" },
     ],
     status: "locked",
     zoneId: "volcanic_depths",