Replace every occurrence of "RBox" with "MyWebdav" in source files, configuration,
legal documents, UI components, and test fixtures. This includes renaming the
`RBoxApp` class to `MyWebdavApp` in the JavaScript component, updating the
TOTP issuer from "RBox" to "MyWebdav" in the auth router, changing the
application description in the argument parser, and updating all user-facing
strings in HTML templates, legal policies, and the manifest file. The
`.env.example` default for `TOTP_ISSUER` is also updated accordingly.
