Build fixes: offline-safe fonts, Next.js API route type updates, TS strict errors resolved, MUI import cleanup, chat markdown wrapper, Azure OpenAI typing, caching key + chapter API id types, and misc error-logging typings.

lib/cache/index.ts

@@ -57,7 +57,7 @@ export class CacheManager {
   }
 
   // Helper methods for specific cache patterns
-  static getChapterKey(bookId: number, chapterNum: number): string {
+  static getChapterKey(bookId: string, chapterNum: number): string {
     return `chapter:${bookId}:${chapterNum}`
   }
 
@@ -68,4 +68,4 @@ export class CacheManager {
   static getUserBookmarksKey(userId: string): string {
     return `bookmarks:${userId}`
   }
-}
+}