feat: implement Cohort entity and DTO with environment variable exclusion in gitignore

.gitignore

@@ -37,3 +37,7 @@ lerna-debug.log*
 
 # Local agent customization
 .agent.md
+
+# Environment variables
+.env.local
+.env

src/modules/cohort/cohort.entity.ts

@@ -12,6 +12,9 @@ export class Cohort {
   @PrimaryGeneratedColumn('uuid')
   id: string;
 
+  @Column({ nullable: true })
+  scopeType: string;
+
   @Column()
   name: string;
 

src/modules/cohort/dto/create-cohort.dto.ts

@@ -5,6 +5,10 @@ export class CreateCohortDto {
   @IsNotEmpty()
   name: string;
 
+  @IsString()
+  @IsOptional()
+  scopeType?: string;
+
   @IsString()
   @IsOptional()
   description?: string;