[Feature] Rename fuzzy_check max_score to hits_limit for clarity

[Feature] Rename fuzzy_check max_score to hits_limit for clarity

The option name max_score was confusing as it doesn't refer to the
symbol score but rather the number of fuzzy hash hits at which the
normalized score reaches ~1.0 (formula: tanh(e * hits / hits_limit)).

- Rename max_score -> hits_limit in fuzzy_check.c and default config
- Add backward compatibility: max_score is still accepted as an alias
- Add lua_cfg_transform to handle legacy configs (max_score overrides
  hits_limit to ensure local.d overrides work correctly)
- Add explanatory comments in config and documentation