Fix unhandled case in module_from_template

### Current Situation

Currently we do not handle the case where the target-file already exists in `module_from_template`:

https://github.com/idom-team/idom/blob/0bf58771ac9fe0fa04853fbc33a2fdf614aaaed3/src/idom/web/module.py#L144-L150

### Proposed Actions

Add a `replace_existing` option and raise an error if it is False and the target file exists.

### Work Items

_No response_