Architecture: Extract all curses-java theme data into JSON format

[sfloess]

Part of #233: Architecture: Unify curses-java and curses-themes with shared implementation

Scope

After the prototype (Borland3D) proves out, extract all remaining themes from hardcoded Java to JSON files.

Tasks

• Convert all 11+ themes to JSON format:
  • Borland, Borland3D, DBase3, DBase4, DBase4_3D, DOS, TRS-80, TI-99/4A, and others
• Validate each JSON file against the canonical schema
• Update curses-java to load all themes from JSON via the JsonThemeLoader
• Verify rendering output matches for every theme
• Deprecate hardcoded theme classes (or keep as fallback during transition)

Acceptance Criteria

• All themes have corresponding validated JSON files
• All themes render identically when loaded from JSON
• Theme JSON files are stored in a well-defined location (e.g., src/main/resources/themes/)
• No regressions in existing tests