feat(billing): cap each owner's stored file volume

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/api/src/conversations/dto.ts

@@ -1,9 +1,13 @@
+import { Type } from 'class-transformer';
 import {
   IsArray,
   IsBoolean,
+  IsInt,
   IsOptional,
   IsString,
+  Max,
   MaxLength,
+  Min,
   MinLength,
   ArrayMinSize,
   ArrayMaxSize,
@@ -32,6 +36,14 @@ export class UpdateConversationSettingsDto {
   downloadUrl?: string;
 }
 
+export class ConversationFileBytesDto {
+  @Type(() => Number)
+  @IsInt()
+  @Min(1)
+  @Max(100 * 1024 * 1024)
+  bytes!: number;
+}
+
 export class CreateConversationDmDto {
   @IsString()
   @MinLength(1)