feat(todo): redesign task detail modal + add inline subtasks

- Redesign TaskEditModal as a multi-column page-like layout:
  - Title (large, borderless textarea with autoGrow)
  - Content grid: description (left) | subtasks + links (right)
  - Props strip: all metadata as horizontal flex-wrap cells (status,
    priority, due date, recurrence, tags, assignee, story points, etc.)
  - No sidebar, no scrollable property list
- Remove redundant `notes` field from TaskMetadata (keep only `description`)
- Remove all legacy migration code from useTaskForm composable
- Add inline subtasks display to TaskItem on the homepage:
  - Shown indented under parent task when task has subtasks and is incomplete
  - Each subtask is directly checkable (toggleSubtask via onSave callback)
  - Vertical connecting line via CSS pseudo-element

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/todo/packages/shared/src/types/task.ts

@@ -20,7 +20,6 @@ export interface EffectiveDuration {
 }
 
 export interface TaskMetadata {
-	notes?: string;
 	attachments?: string[];
 	linkedCalendarEventId?: string | null;
 	// Agile/Productivity metadata