Janik von Rotz 01c3a74954 feat: add global flag to create-dotenv and change default storage location ...

- Modify `bin/create-dotenv` to store `.env` files in the current directory by default.
- Add `-g` / `--global` flag to store files in `TASK_DOTENV_DIR` instead.
- Remove hard-coded `secrets` template special case for path selection; encryption now depends on the filename ending in `secrets.env`.
- Update `docs/library.md`, `task.template`, and `prompt.md` to reflect the new behavior and flag.
- Verify that `remove-dotenv`, `copy-dotenv`, and `rename-dotenv` correctly handle both local and global paths.