Implement: Task Management

[rubenvdlinde]

OpenSpec Change: task-management

Spec path: openspec/changes/task-management

Generated from Specter (6 features).

[rubenvdlinde]

Hydra Builder — Implementation Complete

PR created: #253

All task management components have been implemented with proper SPDX headers and spec traceability:

• TaskList with filtering (status, assignee, priority) and search
• TaskDetail with lifecycle transition error messages
• TaskCreateDialog with case reference validation
• Task validation, lifecycle, and helper utilities

Ready for review.