This commit introduces a `ConversationHandler` for the `/vik` command, replacing the previous simple command.
The new implementation provides an interactive menu for users with admin permissions to:
- View their tasks from a hardcoded project (ID 1).
- Add new tasks to the same project.
The changes include:
- A new `ConversationHandler` in `app/modules/vikunja.py` to manage the interactive flow.
- Integration of the new handler in `app/main.py`.
- Removal of the old `/vik` command handler.
- A fix in `test_vikunja.py` to correctly load environment variables.
