refactor(AppConfig): readability improvements for loadConfig()

[joshtrichards]

• Resolves: #

Summary

Refactors AppConfig::loadConfig() for readability and maintainability without changing intended behavior.

What's changed

• Improved variable names for intent clarity
• Extracted some logic into helper methods
• Added defensive shape checks
• Added/tightened comments/docblocks

Why

• Makes loadConfig() easier to reason about and review.
• Isolates cache hydration and query construction.
• Preserves behavior/performance characteristics
• Minor: Adds robustness against malformed/partial local-cache payloads.

TODO

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI