[OCISDEV-388] Renaming a resource to its current name fails without meaningful error message

## Is your feature request related to a problem? Please describe.
When attempting to rename a file or resource using the same name it already has, the operation fails as expected — however, the error message provided is not informative and does not explain why the operation failed. It just gives

which is very hard to understand for normal user

## Describe the solution you'd like
Renaming a file to its current name should either:
- Succeed silently (no-op), or
- Fail with a clear and specific error message (e.g., "Source and destination names are the same. No action taken.")

## Setup
```
- Web version: `ownCloud Web UI 12.1.0`
- oCIS version: `Infinite Scale 7.3.0-rc.1 Community`
- browser: Firefox
```