Synchronization error when custom photo name string contains space at start of the filename

[RastoHu]

Description
If a space is located in the "middle" of a custom photo name string, the mobile app encounters a synchronization error when trying to sync to the server. This issue occurs when the space is not at the beginning or end of the string, but at the start of the filename.

Environment
Staging

Application (+ app version, build, operating system)

• Android mobile app, replicable also on iOS devices
• App build: 687611

Steps to reproduce

1. Open QGIS with Mergin Maps plugin
2. Configure custom photo name setting with a string containing a space at the start of the filename, for example:
   'sa ni*tized/' + ' f<i>l?e:n\"a:m|e.ext" ' + '-' || now()
3. Open Mergin Maps mobile app on a mobile device
4. Record a feature with a photo using this custom naming configuration
5. Attempt to synchronize the project to the server

Actual results

• Synchronization fails when space appears at the start of the filename of the custom photo name string
• Example failing case: ' f
• Error occurs during sync process to server

Expected results

• Custom photo name should be properly sanitized when the file name starts with a space
• All valid custom photo name configurations should sync successfully

Screenshots or logs

Conclusion
Created by GitHub Copilot and supervised by a human test analyst.

[harminius]

Didn't test it but I also suspect trailing dot to penetrate the regex and hit the pathvalidate shield...

[tomasMizera]

You can find the builds to test here: #4229 (comment)

[IvaKuklica]

Retesting completed
The fix works as expected and all tests passed on all relevant applications.

Application (+ app version, build, operating system):
🤖 Android: Samsung Galaxy A53 / Android 15 - build 733911
🍎 iOS: ios 26.1 / build 25.11.828011
🪟 Win: Exe from artefacts here