Feature Request: In-App .ics (iCalendar) File Import for Quick Task Creation

### Describe your improvement idea or feature request

Currently, to add tasks from external calendars or event invitations, users must manually type out the details, due dates, and descriptions into Taskwarrior.

This feature request is to add native `.ics` file parsing into the Flutter app. Users will be able to select an `.ics` file from their device storage, parse the included `VEVENT` and `VTODO` items, preview the tasks, and selectively merge them safely into either the Standard local database or the Task Server Replica.

### How would you like to see it implemented?

1. Go to the Home screen and click on the **'+'** FAB to open the Add Task bottom-sheet.
2. Click on a newly added **'Import ICS'** icon button.
3. This triggers a native File Picker allowing the user to select any `.ics` file from their Android/iOS device.
4. A secondary `IcsImportBottomSheet` appears listing all the detected tasks parsed from the file with selectable checkboxes.
5. Click **'Import'** to merge the selected tasks. The code will safely route the parsed tasks to `Replica.addTaskToReplica` if the user is using the Task Server, or use the standard `taskParser` and `mergeTask` otherwise.

### Put here any screenshots or videos (optional)

_No response_

### How can we contact you (optional)

You can tag me right here on GitHub, or reach me on Zulip (User ID: 1017036).

### Would you like to work on this issue?

Yes

### By submitting this issue, I have confirmed that:

- [x] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.

Inizia dalla Home screen, dal '+' FAB e dal bottom-sheet Add Task, quindi segui l'entry point proposto per l'importazione ICS e IcsImportBottomSheet. Esamina Replica.addTaskToReplica, taskParser e mergeTask. Il lavoro è completato quando è possibile selezionare un file .ics, visualizzare in anteprima gli elementi VEVENT/VTODO, importarli selettivamente e indirizzarli al percorso di archiviazione appropriato.

Scritto dal modello di indicizzazione a partire dal testo della issue.