Add client version mode support to enable version-specific behavior:
- Add Mode type with constants for all game versions (S1.0 through ZZ)
- Add ClientMode (string) and RealClientMode (Mode) to Config
- Add ClanMemberLimits to GameplayOptions for configurable clan sizes
- Add MaximumFP to GameplayOptions for festa points cap
- Parse ClientMode string to RealClientMode enum in LoadConfig
- Set sensible defaults (ZZ for mode, standard limits for clans)
- Update config.example.json with new fields
This enables cherry-picking version-specific fixes from main branch.
- Renamed config key from GuildMealDuration to ClanMealDuration
- Changed unit from minutes to seconds (matching upstream convention)
- Updated handler to use seconds-based calculation
- Updated documentation and examples
This fixes the bug where clan meals were not being shared between
guild members when using a config.json with the upstream naming.
