Implements the core savePartialSettings method that:
- Validates fields against UI_EDITABLE_FIELDS whitelist
- Deep merges partial updates with current settings
- Creates backup before saving
- Restores backup on save failure
- Reloads .env file to populate cache with correct keys
Added comprehensive tests:
- Partial update preserves existing fields
- Rejects non-whitelisted fields
- Handles nested object updates
- Restores backup on save failure
Fixed cache key inconsistency bug by clearing cache in loadEnvFile()
and reloading after save to ensure proper cache population.
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
f3be0ad01d