feat: add notification triggers, comment roles, mention list, and static file serving

- Notify users on ticket assignment and remittance confirm/reject
- Add collector role to comment endpoints
- Add /users/mention-list endpoint for @mention support
- Serve uploaded files via express.static

src/user/user.service.ts

@@ -51,6 +51,16 @@ export class UserService {
     return users.map((u) => this.formatUser(u));
   }
 
+  async findForMention(tenantId: string) {
+    const db = this.prisma.forTenant(tenantId);
+    const users = await db.user.findMany({
+      where: { isActive: true },
+      select: { id: true, firstName: true, lastName: true },
+      orderBy: { firstName: 'asc' },
+    });
+    return users;
+  }
+
   async findById(tenantId: string, userId: string) {
     const db = this.prisma.forTenant(tenantId);
     const user = await db.user.findFirst({