Rename the frontend parsing module from `parseTaskText` to `quickAddMagic`
for clarity. The module handles much more than text parsing — it's the
core of the quick add magic feature. This rename makes its purpose
immediately obvious and aligns with how the feature is referenced
throughout the UI and documentation.
No logic changes — only directory/file renames and import updates.
Because the tasks were emitted as the relation was created, when a task had multiple subtasks the parent was emitted multiple times and thus, shown multiple times in the list view. This change fixes that behaviour by emitting all tasks at the end, when all relations are created.
This change allows to specify the task index when creating a task, which will then be checked to avoid duplicates and used. This allows us to calculate the indexes for all tasks beforehand when creating them at once using quick add magic.
The method is not bulletproof, but already fixes a problem where multiple tasks would have the same index when created that way.
Resolves https://community.vikunja.io/t/add-multiple-tasks-at-once/333/16