feat: implement pipeline feature for automated workflow steps

- Introduced a new pipeline service to manage custom workflow steps that execute after a feature is marked "In Progress".
- Added API endpoints for configuring, saving, adding, updating, deleting, and reordering pipeline steps.
- Enhanced the UI to support pipeline settings, including a dialog for managing steps and integration with the Kanban board.
- Updated the application state management to handle pipeline configurations per project.
- Implemented dynamic column generation in the Kanban board to display pipeline steps between "In Progress" and "Waiting Approval".
- Added documentation for the new pipeline feature, including usage instructions and configuration details.

This feature allows for a more structured workflow, enabling automated processes such as code reviews and testing after feature implementation.

libs/types/src/index.ts

@@ -105,3 +105,11 @@ export type {
   BacklogPlanRequest,
   BacklogPlanApplyResult,
 } from './backlog-plan.js';
+
+// Pipeline types
+export type {
+  PipelineStep,
+  PipelineConfig,
+  PipelineStatus,
+  FeatureStatusWithPipeline,
+} from './pipeline.js';

libs/types/src/pipeline.ts

@@ -0,0 +1,28 @@
+/**
+ * Pipeline types for AutoMaker custom workflow steps
+ */
+
+export interface PipelineStep {
+  id: string;
+  name: string;
+  order: number;
+  instructions: string;
+  colorClass: string;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface PipelineConfig {
+  version: 1;
+  steps: PipelineStep[];
+}
+
+export type PipelineStatus = `pipeline_${string}`;
+
+export type FeatureStatusWithPipeline =
+  | 'backlog'
+  | 'in_progress'
+  | 'waiting_approval'
+  | 'verified'
+  | 'completed'
+  | PipelineStatus;