Delete task with confirmation #133

Description

Allow users to delete a task from the Task Detail screen by tapping the "Delete" button. Since deletion is destructive and irreversible, a confirmation dialog must be shown before the task is actually deleted.

The confirmation dialog should clearly state what will be deleted and offer two actions: "Delete" (destructive, confirms) and "Cancel" (dismisses the dialog). Upon confirmation, the task is removed from the repository and the user is navigated back to the previous screen.

Depends on #129 (Task detail screen).

Scope

In scope: delete confirmation dialog, task deletion from the repository, navigation back after deletion, and string resources.

Out of scope: undo/restore deleted task, swipe-to-delete (separate ticket), batch deletion.

Acceptance criteria

• GIVEN the user is on the Task Detail screen
  WHEN they tap the "Delete" button
  THEN a confirmation dialog is shown
• GIVEN the confirmation dialog is shown
  WHEN the dialog renders
  THEN it clearly states that the task will be permanently deleted
• GIVEN the confirmation dialog is shown
  WHEN the user taps "Cancel"
  THEN the dialog is dismissed and the task is not deleted
• GIVEN the confirmation dialog is shown
  WHEN the user taps "Delete"
  THEN the task is removed from the repository and the user is navigated back to the previous screen
• GIVEN the user has confirmed deletion
  WHEN they return to the previous screen
  THEN the deleted task is no longer visible in the task list
• GIVEN user-visible text appears in the confirmation dialog
  WHEN the app renders the dialog
  THEN all visible text comes from string resources