feat: Phase 2 - Tasks CRUD API, kanban/list UI, dialogs, activity feed, keyboard shortcuts

- Tasks REST API under /api/domains/[domainId]/tasks/ with full CRUD, filtering, pagination
- Complete/uncomplete endpoints
- Bulk update endpoint for drag-to-reorder
- Dependencies API with cycle detection
- Tags API for task tagging
- Activity feed API scoped to workspace
- Updated kanban board view with 4 columns (todo/in_progress/done/cancelled)
- Updated list view with status column and workspace-scoped API calls
- Task create dialog with title, description, status, priority, due date, estimate
- Task detail panel (sheet) with full edit capabilities
- Task activity feed widget
- Keyboard shortcuts: c t (new task), e (edit), d (delete), Space (open), Esc (close), 1-4 (filter)
- All routes follow AGENTS.md contract: Drizzle writes + activity feed + pg_notify

apps/web/app/api/domains/[domainId]/tasks/[id]/complete/route.ts

@@ -0,0 +1,47 @@
+// AGENT INSTRUCTION: After every write (INSERT/UPDATE/DELETE), you MUST:
+// 1. Insert activity feed entry
+// 2. Call pg.notify('project_e_events', JSON.stringify({ type, action, id, workspace_id }))
+// See AGENTS.md for full rules.
+
+import { NextRequest, NextResponse } from 'next/server';
+import { withAuth, requireWorkspaceAccess, createErrorResponse } from '@/lib/auth';
+import { recordActivity } from '@/lib/activity';
+import { db, tasks } from '@project-e/db';
+import { and, eq, isNull } from 'drizzle-orm';
+
+type RouteContext = { params: Promise<{ domainId: string; id: string }> };
+
+// POST /api/domains/[domainId]/tasks/[id]/complete — Mark task as done
+export const POST = withAuth<RouteContext>(async (request: NextRequest, user, context) => {
+  const { domainId, id } = await context!.params;
+  await requireWorkspaceAccess(domainId);
+
+  const [existing] = await db.select()
+    .from(tasks)
+    .where(and(eq(tasks.id, id), eq(tasks.domainId, domainId), isNull(tasks.deletedAt)))
+    .limit(1);
+
+  if (!existing) {
+    return createErrorResponse('NOT_FOUND', 'Task not found', 404);
+  }
+
+  const [updated] = await db.update(tasks)
+    .set({
+      status: 'done',
+      completedAt: new Date(),
+      updatedAt: new Date(),
+    })
+    .where(eq(tasks.id, id))
+    .returning();
+
+  await recordActivity({
+    actor: user.name,
+    action: 'completed',
+    entityType: 'task',
+    entityId: id,
+    changes: { previousStatus: existing.status },
+    workspaceId: domainId,
+  });
+
+  return NextResponse.json(updated);
+});