chore(tasks): update task UI

[Rishavraaj]

Summary

• Task UI overhaul — updated the tasks table with new columns (ID with copy-to-clipboard, Subtasks count, Created By), replaced the Created At column with Completed At,
  and improved status/assignee inline editing
• Task owner tracking — added task_owner table to record who created a task; on creation the authenticated user is automatically saved as the primary owner via a DB
  transaction
• Removed created_by text field — owner identity is now properly tracked through the task_owner relation instead of a free-text column
• Pagination fix — tasks list now fetches up to 100 tasks in one request and delegates pagination to the client-side table, fixing subtask row count mismatch
• ResizeObserver mock — added to test setup to unblock frontend tests in jsdom

Changes by area

Backend

• Added TaskOwner model in core.prisma (mirrors ContactOwner/CompanyOwner/DealOwner pattern) with task_id, user_id, is_primary, assigned_at, unique constraint
  on (task_id, user_id), and cascade deletes
• TaskRepository.create() runs in a $transaction — creates the task then inserts a task_owner row with is_primary = true
• All task queries now include owners with user id, name, email
• Dropped created_by column from the task table

Frontend

• New IdCell component — shows task ID, copies to clipboard on click with "Copied" feedback
• New Subtasks column — shows badge with count for parent tasks, — for subtasks/empty
• Created By column replaces Created At
• BaseTable now manages internal pagination state when none is provided externally
• autoResetPageIndex: false added to prevent table jumping on data updates
• Removed SidebarDivider entries from the app layout

Tests

• Unit tests for all createTaskColumns cell renderers (ID, Title, Subtasks, Status, Assignee, Created By, Completed At, Actions)
• Controller spec updated to pass req argument to create

Test plan

• Create a task — verify a task_owner row is created with is_primary = true for the logged-in user
• Task list shows ID, Subtasks, Created By, Completed At columns correctly
• Click a task ID — verify it copies to clipboard and shows "Copied" feedback
• Inline status change to DONE sets completedAt; changing away clears it
• Inline assignee edit saves on blur and Enter, reverts on Escape
• Delete a task — verify task_owner is cascade deleted
• Pagination works correctly across multiple pages of tasks