feat: add main questline / overarching story system (#24)

- 22 chapters across the full game arc (18 zone bosses + 4 milestones)
- Choice-based narrative with {characterName} dynamic substitution
- Story progress (unlocked + completed chapters) is permanent across all resets
- Server-side anti-cheat: chapters/choices can only accumulate, never be removed
- Tab badge and lower-right toast notifications for newly unlocked chapters
- Story choices displayed on the Character Sheet and Character Page
- How to Play entry added to About panel

apps/api/src/services/transcendence.ts

@@ -80,6 +80,8 @@ export const buildPostTranscendenceState = (
     transcendence: newTranscendenceData,
     // Apotheosis data is eternal — never wiped by transcendence
     ...(currentState.apotheosis ? { apotheosis: currentState.apotheosis } : {}),
+    // Story chapter progress is permanent — survives all resets
+    ...(currentState.story ? { story: currentState.story } : {}),
   };
 
   return { newState, newTranscendenceData, echoesEarned };