Racer positional magic (source of truth from libconfig)

[SergeantSerk]

Aligns the server's magic item selection logic with the official database tables in libconfig_c.dat and resolves key allocation bugs.

Key Changes:

• Table Alignments:
  • Implemented separate solo group ratios (MagicGroupRatio) and team group ratios (MagicGroupTeamRatio)
  • Updated base slot probabilities to match Table 199 and Table 217 exactly
  • Added slot-level team modifiers (MagicSlotTeamModifier) for trailing assistance items
• Rank Normalization: Remaps player rank linearly onto the [1, 8] table columns to ensure last-place racers in small lobbies consistently scale to rank 8 weights

This implementation is far more comprehensive and extensive, using source of truth from libconfig_c.dat itself, in contrast to PR #271 which is a simple weights distribution implementation, based on community survey.