Implement "Share to Taskwarrior" (receive sharing intent)

### Describe your improvement idea or feature request

Currently, the app cannot receive shared text or URLs from other applications via the system Share Sheet. This is a good feat for quickly capturing tasks (e.g., sharing a URL from a browser to creating a "Read this" task).

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

- Integrate the receive_sharing_intent (or similar) package.

- Configure Android Manifest and iOS Info.plist to accept text/plain share intents.

- Handle the incoming intent by navigating to the "Add Task" screen and pre-filling the description field with the shared text/URL.

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

Yes

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