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.

app/api/debug/user/route.ts

@@ -38,6 +38,6 @@ export async function POST(request: Request) {
     })
   } catch (error) {
     console.error('User debug error:', error)
-    return NextResponse.json({ error: 'Debug failed', details: error.message }, { status: 500 })
+    return NextResponse.json({ error: 'Debug failed', details: (error as any)?.message || error }, { status: 500 })
   }
-}
+}