feat(api): pipeline merge preview and merge endpoints

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

apps/api/src/pipelines/pipelines.controller.ts

@@ -17,6 +17,7 @@ import type { Actor } from '../common/record-scope';
 import {
   CreatePipelineDto,
   CreatePipelineStageDto,
+  MergePipelineDto,
   ReorderPipelineStagesDto,
   UpdatePipelineStageDto,
 } from './dto';
@@ -49,6 +50,25 @@ export class PipelinesController {
     return this.pipelinesService.create(user.organizationId, dto.name);
   }
 
+  @Get(':pipelineId/merge-preview')
+  @Roles('owner', 'admin')
+  mergePreview(
+    @CurrentUser() user: { organizationId: string },
+    @Param('pipelineId') pipelineId: string,
+  ) {
+    return this.pipelinesService.mergePreview(user.organizationId, pipelineId);
+  }
+
+  @Post(':pipelineId/merge')
+  @Roles('owner', 'admin')
+  merge(
+    @CurrentUser() user: { organizationId: string },
+    @Param('pipelineId') pipelineId: string,
+    @Body() dto: MergePipelineDto,
+  ) {
+    return this.pipelinesService.merge(user.organizationId, pipelineId, dto);
+  }
+
   @Post(':pipelineId/stages')
   @Roles('owner', 'admin')
   createStage(