fix: `os runtime php update-setting` silently fails when adding a setting that does not exist

[alehostert]

Summary

The os runtime php update-setting command looks like it only modifies settings that already exist in the phpIniOverride block. When the setting does not exist, the command returns "status": "success" without inserting it, creating a false impression that the operation succeeded.

Steps to reproduce

1. Update an EXISTING setting — works correctly

root@f2ccb3e81c08:/infinite# grep session.gc_maxlifetime /app/conf/php-webserver/primary.conf
php_value session.gc_maxlifetime 1800

root@f2ccb3e81c08:/infinite# os runtime php update-setting --name session.gc_maxlifetime --value 1440 --version 8.2
{
  "status": "success",
  "body": "PhpConfigsUpdated",
  "readableMessage": ""
}

root@f2ccb3e81c08:/infinite# grep session.gc_maxlifetime /app/conf/php-webserver/primary.conf
php_value session.gc_maxlifetime 1440
# Result: setting updated from 1800 to 1440 ✅

2. Add a NON-EXISTENT setting — returns success but does nothing

root@f2ccb3e81c08:/infinite# grep session.gc_probability /app/conf/php-webserver/primary.conf
root@f2ccb3e81c08:/infinite# 
root@f2ccb3e81c08:/infinite# os runtime php update-setting --name session.gc_probability --value 1 --version 8.2
{
  "status": "success",
  "body": "PhpConfigsUpdated",
  "readableMessage": ""
}

3. Verify — setting was not added

root@f2ccb3e81c08:/infinite# grep session.gc_probability /app/conf/php-webserver/primary.conf
root@f2ccb3e81c08:/infinite# 

Expected behavior

• If the setting does not exist in phpIniOverride: insert the new php_value line
• If the setting exists: update the value
• If the operation cannot be completed: return an explicit error instead of "status": success

Impact

Operators relying on update-setting to apply configuration changes may believe the fix was applied when it was not. This leads to unresolved issues persisting in production without any indication of failure.

Related: goinfinite/os-services#73 — session.gc_probability missing from default phpIniOverride template