Add license resolution utilities and integrate license information into model metadata processing. The changes include:
- Add `resolve_license_payload` function to extract license data from Civitai model responses
- Integrate license information into model metadata in CivitaiClient and MetadataSyncService
- Add license flags support in model scanning and caching
- Implement CommercialUseLevel enum for standardized license classification
- Update model scanner to handle unknown fields when extracting metadata values
This ensures proper license attribution and compliance when working with Civitai models.
- Add metadata_source field to track origin of model metadata
- Define MODEL_COLUMNS constants for consistent column management
- Refactor SQL queries to use dynamic column selection
- Improve Civitai data detection to include creator_username and trained_words
- Update database operations to handle new metadata field and tag management
