Add support for Nextcloud Dashboard app integration

[vitormattos]

Is your feature request related to a problem? Please describe.

No response

Describe the solution you'd like

Description:

We want to integrate LibreSign with the Nextcloud Dashboard app by implementing a widget that displays recent signed or uploaded files by date. This will improve usability and provide quick access to important documents directly from the Nextcloud home screen.

🔍 Additional notes:

• The widget should fetch files grouped or sorted by creation date by default.
• Future enhancements may include filters by status or file type.

This issue is open to contributors. If you're interested, feel free to leave a comment or open a draft PR to get started!

Describe alternatives you've considered

📚 Reference Documentation:

• Nextcloud Dashboard App Developer Guide:
  https://docs.nextcloud.com/server/latest/developer_manual/digging_deeper/dashboard.html
• LibreSign API endpoint (to list files by date):
  https://docs.libresign.coop/developer_manual/api.html#/file/file-list

Additional context

🛠️ Expected tasks:

• Create a Dashboard widget class that implements the IWidget interface.
• Use the https://docs.libresign.coop/developer_manual/api.html#/file/file-list endpoint to fetch recent files.
• Display file titles, creation dates, and status (e.g. signed, pending).
• Make sure the widget is responsive and follows the Nextcloud design guidelines.
• Use the localization methods to send the English text to Transifex
• Write tests
• Update the user documentation adding instructions about this feature: https://docs.libresign.coop