fix(service): correctly parse [Auth] and [Capture] sections

[Vladush]

Description

Fixes a critical issue where configuration settings in the [Auth] and [Capture] sections of config.ini were being ignored by the service.

Specific Changes

• src/service/config.cpp: Updated load_config() to explicitly look for keys in Auth.* and Capture.*.
• Backward Compatibility: Added fallback logic to check General.* if Auth.* keys are missing, ensuring existing configuration files continue to work.
• New Features: Enabled parsing of enroll_hdr, enroll_averaging, and enroll_average_frames from the global [Capture] section.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual Verification: built the service and verified via logs that it correctly picked up Auth.threshold = 0.42 set in config.ini (previously stuck at default).
• Regression Test: Verified that General.threshold still works if [Auth] is missing (logic check).

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation (covered in PR docs: audit and fix documentation consistency #25)
• My changes generate no new warnings
• New and existing unit tests pass locally with my changes