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/specs/dashboard/spec.md

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+# Dashboard Capability
+
+Provides users with an at-a-glance overview of their work, project health, and system statistics.
+
+## ADDED Requirements
+
+### Requirement: Dashboard Statistics
+
+The system SHALL display aggregated statistics showing the user's task overview.
+
+#### Scenario: User views task statistics
+- Given: User is authenticated
+- When: User navigates to Dashboard
+- Then: System displays:
+  - Total tasks assigned to user
+  - Tasks due this week
+  - Overdue tasks count
+  - Completion rate percentage
+
+### Requirement: My Workload Widget
+
+The system SHALL display the current user's workload summary for the current week.
+
+#### Scenario: User views personal workload
+- Given: User is authenticated
+- When: User views Dashboard
+- Then: System displays:
+  - Allocated hours vs capacity hours
+  - Load percentage with visual indicator
+  - Load level status (normal/warning/overloaded)
+
+### Requirement: Project Health Summary
+
+The system SHALL display an aggregated project health summary.
+
+#### Scenario: User views project health overview
+- Given: User is authenticated
+- When: User views Dashboard
+- Then: System displays:
+  - Total projects count
+  - Healthy/At-Risk/Critical breakdown
+  - Average health score
+  - Projects with blockers count
+
+### Requirement: Quick Actions
+
+The system SHALL provide quick navigation links to common actions.
+
+#### Scenario: User accesses quick actions
+- Given: User is authenticated
+- When: User views Dashboard
+- Then: System displays navigation links to:
+  - Spaces page
+  - Workload page
+  - Project Health page
+  - (Admin only) Audit page
+
+### Requirement: Dashboard API Endpoint
+
+The backend SHALL provide a single aggregated endpoint for dashboard data.
+
+#### Scenario: Frontend fetches dashboard data
+- Given: User is authenticated
+- When: Frontend requests GET /api/dashboard
+- Then: Backend returns:
+  - User task statistics
+  - Current week workload summary
+  - Project health summary
+- And: Response is optimized with single database query where possible