feat: Kanban board with five-column view, drag-and-drop, detail drawer, anomaly detection (Phase 7)

Backend: new kanban API with mock data, five-column task aggregation, task detail, drag-to-move
with block reason validation, and server-side anomaly detection (blocked_timeout, unclaimed,
retry_failure).

Frontend: full kanban page with summary bar + filters, five-column board with BLOCKED orange
border, task cards with color-coded left bar and anomaly highlighting, HTML5 native drag-and-drop
(desktop only), block reason modal, done confirmation, 480px detail drawer with meta/description/
dependencies/activity timeline, floating batch operations bar, and optimistic updates with rollback.

Drawer component: title prop changed from string to ReactNode to support rich title content.

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/main.py

@@ -4,7 +4,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.database import engine, Base
-from app.api import auth, users, audit, dashboard, gateway, health, cron, keys
+from app.api import auth, users, audit, dashboard, gateway, health, cron, keys, kanban
 from app.middleware.audit import AuditMiddleware
 
 
@@ -38,6 +38,7 @@ app.include_router(dashboard.router, prefix="/api/v1")
 app.include_router(gateway.router, prefix="/api/v1")
 app.include_router(health.router, prefix="/api/v1")
 app.include_router(cron.router, prefix="/api/v1")
+app.include_router(kanban.router, prefix="/api/v1")
 app.include_router(keys.router, prefix="/api/v1")