Improve WebDAV Error Handling with Custom Error Message and Automatic Patch Execution

### Please agree to the following

- [x] I have searched [existing issues](https://github.com/cryptomator/cryptomator/issues?q=) for duplicates
- [x] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/cryptomator/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

Show a custom error message for WebDAV issues and offer an option to automatically run patchWebDAV.ps1

### Motivation

Users on Windows frequently encounter WebDAV-related issues when unlocking a vault, as seen in [Discussion #3410](https://github.com/cryptomator/cryptomator/discussions/3410). Currently users must manually run patchWebDAV.ps1 to fix them.

This feature request proposes:
- Custom Error Handling: Instead of displaying a generic error, Cryptomator should show a detailed message explaining the WebDAV issue and offering a solution.
- Automatic Execution of patchWebDAV.ps1: If the issue is detected, the application should prompt users to run the patch with administrator privileges.

### Considered Alternatives

_No response_

### Anything else?

_No response_

Start by tracing the Windows WebDAV failure during vault unlocking and reviewing patchWebDAV.ps1 alongside Discussion #3410. Define the user-facing error details and the administrator prompt flow; done means the detected issue explains the fix and offers to run the patch.

Written by the indexing model from the issue text.