feat: post-prestige automation (auto-adventurer) (#76)

## Summary

Closes #61

- Adds the **Autonomous Recruitment** prestige upgrade (50 runestones) to both the API and web data files
- Adds `autoAdventurer?: boolean` to the `GameState` type for backwards-compatible saves
- Adds tick-loop logic in GameContext that automatically purchases the highest-tier unlocked adventurer the player can afford each frame when the toggle is enabled
- Adds `toggleAutoAdventurer` callback and exposes it through the context
- Adds toggle UI in the Prestige Shop (mirrors the existing Auto-Prestige toggle pattern)
- Updates the How to Play guide in the About panel to document the new automation feature

✨ This issue was created with help from Hikari~ 🌸

Reviewed-on: #76
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/web/src/components/game/aboutPanel.tsx

@@ -188,14 +188,16 @@ const howToPlay = [
   },
   {
     body:
-      "Toggle automation in the Quests and Boss Encounters panels! Auto-Quest"
-      + " automatically sends your party on the highest-zone available quest"
-      + " as soon as one completes, skipping quests whose combat power"
-      + " requirement isn't met. Auto-Boss automatically challenges the"
-      + " highest available boss as soon as one is ready. Both can be toggled"
-      + " on or off at any time using the 🤖 Auto button in each panel"
-      + " header.",
-    title: "🤖 Auto-Quest & Auto-Boss",
+      "Toggle automation in the Quests, Boss Encounters, and Prestige Shop"
+      + " panels! Auto-Quest automatically sends your party on the"
+      + " highest-zone available quest as soon as one completes, skipping"
+      + " quests whose combat power requirement isn't met. Auto-Boss"
+      + " automatically challenges the highest available boss as soon as one"
+      + " is ready. Auto-Adventurer (unlocked via the Prestige Shop for 50"
+      + " runestones) automatically purchases the highest-tier adventurer you"
+      + " can currently afford each tick, keeping your income growing after a"
+      + " prestige without any manual clicks.",
+    title: "🤖 Auto-Quest, Auto-Boss & Auto-Adventurer",
   },
   {
     body: