feat: add OPC (One Person Company) management system with Kanban board

Phase 1 MVP implementation:
- PostgreSQL database schema for tasks, agents, executions, time tracking
- Backend API: task CRUD, agent management, automatic time tracking
- Frontend: Kanban board with drag-and-drop (Parking Lot → In Progress → Done)
- Task modal for creating/editing tasks with tags, priority, assignee
- 3 core agents seeded: PM, CTO, COO
- Agent approval workflow: CxO level requires approval, others auto-execute
- Automatic time tracking: starts on in_progress, stops on done
- RBAC integration: OPC page accessible to admin/member roles

Features:
- Drag-and-drop tasks between columns
- Assign tasks to humans or AI agents
- Priority badges (low, medium, high, urgent)
- Tags and due dates
- Task history tracking
- Time entry tracking with automatic timer
- Agent execution records with approval workflow

Next steps:
- Initialize OPC database on NAS
- Implement agent executor service
- Add WebSocket for real-time updates
- Add email notifications
- Add PDF invoice generation

gitea/init-opc-db.sql

@@ -0,0 +1,6 @@
+-- Create OPC database if it doesn't exist
+SELECT 'CREATE DATABASE opc'
+WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'opc')\gexec
+
+-- Grant permissions to gitea user
+GRANT ALL PRIVILEGES ON DATABASE opc TO gitea;