feat: implement multi-segment PDF email attachments and add PWA mobile icons

paperless-backend/src/inbox/inbox.controller.ts

@@ -200,7 +200,7 @@ export class InboxController {
       subject: string;
       body: string;
       html?: string;
-      filename?: string;
+      segments: { pages: number[]; filename: string }[];
     },
     @Request() req: any,
   ): Promise<void> {