Extension-generation needs adjustements

The extension-generation process is currently assuming you need encrypted userdata. That should get adjusted like this:
- Add an option to the click annotations like `--encrypted-userdata` here: https://github.com/cryptoadvance/specter-desktop/blob/master/src/cryptoadvance/specter/cli/cli_ext.py#L39 (including adding it as a param to the method signature)
- Add a section explaining what it means and that the extension should decide between encrypted/unencrypted here: https://github.com/cryptoadvance/specter-desktop/blob/master/src/cryptoadvance/specter/cli/cli_ext.py#L111-L112
- Add the variable to the `ExtGen` instantiation and there ...
- The service and the controller would needs some adjustments. They are rendered here: https://github.com/cryptoadvance/specter-desktop/blob/master/src/cryptoadvance/specter/cli/cli_ext.py#L150-L160 however, the code for the templates is living here:
- https://github.com/cryptoadvance/specterext-dummy/blob/master/src/dummyorg/specterext/dummy/service.py#L12
- https://github.com/cryptoadvance/specterext-dummy/blob/master/src/dummyorg/specterext/dummy/controller.py#L53

Mind the different templating syntax. Those are "metatemplates" as they are creating templates which themself are later templates.

You can test it via using `--tmpl-fs-source` and checkout the dummy-project somewhere. Also i've created a small section about https://docs.specter.solutions/desktop/extensions/intro/#virtualenv-management

Start in src/cryptoadvance/specter/cli/cli_ext.py, reading the click options, ExtGen instantiation, and service/controller rendering around the referenced lines. Then inspect the metatemplates in specterext-dummy's service.py and controller.py, paying attention to their different templating syntax. Use --tmpl-fs-source with the dummy project; done means the generated extension handles the documented encrypted or unencrypted userdata choice.

Written by the indexing model from the issue text.