[Bug]: sync files between Mac / windows / Linux

### ⚠️ Before submitting, please verify the following: ⚠️

- [X] This is a **bug**, not a question or a configuration issue.
- [X] This issue is **not** already reported on Github (I've searched it).
- [X] Nextcloud Server and Desktop Client are **up to date**. See [Server Maintenance and Release Schedule](https://github.com/nextcloud/server/wiki/Maintenance-and-Release-Schedule) and [Desktop Releases](https://nextcloud.com/install/#install-clients) for supported versions.
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### Bug description

Is it a bug-report r a feature request.. I think a bit of both.
Some characters (like the ':') are supported on Apple/Mac but not on Windows and the syncing becomes a problem:


Could it be an idea to keep "a little database" within the desktop client that keeps track of those files with "incompatible characters" and replaces them with "_".. so something like:
```
file-ID: 1234
cloud: name:something.csv
local: name_something.csv
```
As long as the file name does not change 'local' you can sync the content normally.
When the file name changes the ':' will get lost.. but at least the contents of the file can be seen & used!
For completeness a warning could be given upon sync, but it would be so much better that when the file does get synced!

### Steps to reproduce

1. create a file on a Mac with a ' : ' in it
2. try and sync it with a PC..

### Expected behavior

see bug description

### Which files are affected by this bug

see bug description

### Operating system

Windows

### Which version of the operating system you are running.

Windows 10

### Package

Appimage

### Nextcloud Server version

27.1.11

### Nextcloud Desktop Client version

3.13.0

### Is this bug present after an update or on a fresh install?

Updated from a minor version (ex. 3.4.2 to 3.4.4)

### Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

### Are you using an external user-backend?

- [ ] Default internal user-backend
- [ ] LDAP/ Active Directory
- [ ] SSO - SAML
- [ ] Other

### Nextcloud Server logs

_No response_

### Additional info

_No response_

Start by reproducing the Mac-to-Windows sync case described in the issue, using a filename containing a colon. Trace how the desktop client handles the incompatible name and define done as preserving usable file contents across platforms, with the proposed renaming behavior and optional sync warning evaluated.

Written by the indexing model from the issue text.