feat: implement dashboard widgets functionality

Backend:
- Add dashboard API router with widget endpoints
- Create dashboard schemas for widget data
- Add dashboard tests

Frontend:
- Enhance Dashboard page with widget components
- Add dashboard service for API calls
- Create reusable dashboard components

OpenSpec:
- Archive add-dashboard-widgets change
- Add dashboard capability specs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openspec/changes/archive/2026-01-07-add-dashboard-widgets/proposal.md

@@ -0,0 +1,38 @@
+# Proposal: add-dashboard-widgets
+
+## Summary
+
+Replace the placeholder Dashboard page with functional dashboard widgets that provide users with an at-a-glance overview of their work and system status.
+
+## Motivation
+
+The current Dashboard displays only a welcome message and placeholder text ("Features will be added as development progresses"). Users need a centralized view of:
+- Their assigned tasks and workload
+- Project health across the organization
+- Quick access to common actions
+- System statistics
+
+## Scope
+
+### In Scope
+- Dashboard statistics cards (my tasks, overdue, completion rate)
+- My workload summary widget (reuses existing `/workload/me` API)
+- Project health summary widget (reuses existing `/projects/health/dashboard` API)
+- Quick actions section with navigation links
+- Backend API endpoint for aggregated dashboard data
+
+### Out of Scope
+- Customizable widget layout (future enhancement)
+- Real-time WebSocket updates for dashboard (can be added later)
+- Dashboard for specific roles (manager vs engineer views)
+
+## Dependencies
+
+Reuses existing APIs:
+- `GET /workload/me` - User workload summary
+- `GET /projects/health/dashboard` - Project health overview
+- `GET /api/projects/{project_id}/tasks` with `assignee_id` filter
+
+## Risk Assessment
+
+**Low Risk** - This change primarily adds a new frontend page using existing backend APIs. A new lightweight aggregation endpoint is added but doesn't modify existing data structures.