fix(leads): keep a future follow-up as an activity on the lead

A scheduled follow-up only stored a date, and activities opened from a lead were not linked back, so they disappeared from the lead.

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

apps/api/src/activities/dto.ts

@@ -364,6 +364,11 @@ export class CreateActivityDto {
   @IsString()
   dealId?: string | null;
 
+  @IsOptional()
+  @ValidateIf((_, v) => v !== '' && v != null)
+  @IsString()
+  leadId?: string | null;
+
   @IsOptional()
   @ValidateIf((_, v) => v !== '' && v != null)
   @IsString()
@@ -459,6 +464,11 @@ export class UpdateActivityDto {
   @IsString()
   dealId?: string | null;
 
+  @IsOptional()
+  @ValidateIf((_, v) => v !== '' && v != null)
+  @IsString()
+  leadId?: string | null;
+
   @IsOptional()
   @ValidateIf((_, v) => v !== '' && v != null)
   @IsString()