Gromulus v1.5: user metadata save workflow, schema expansion, and UI refactor

- Added user-editable game metadata workflow with explicit Save button (no autosave).
- Added dirty-state tracking and Save/Discard/Cancel prompts when navigating away or closing with unsaved changes.
- Added DB schema support for new metadata fields:
  - 
  - , 
  - , 
  - , 
  - , 
- Wired UI to user-first metadata precedence with  fallback for release date, genre, cooperative, max players, and description.
- Added release date display/storage conversion:
  - GUI display 
  - DB storage 
- Refactored main game info panel:
  - moved hash/file/No-Intro/TOSEC detail fields into  modal
  - added compact TOSEC/NoIntro match indicators
  - added Favorite, Release Date, Genre, Cooperative, Max Players, Description, and User Notes controls
- Enhanced artwork previews from prior update:
  - larger preview boxes
  - aspect-ratio-preserving scaling
  - click-to-open full-size modal viewer
- Updated schema/documentation files to stay aligned:
  - 
  - 
  - canonical DB utility schema/migration logic