refactor(player): encapsulate game state behind PlayerSettings, clear VisibilityModifier and HiddenField

- ParkourUser/ParkourPlayer/GeneratorState public mutable fields -> private + short accessors
- per-player settings extracted to player/data/PlayerSettings (ParkourPlayer 188 -> 96 lines,
  PMD-counted methods 20 -> 9); this is what fixed the TooManyMethods violation that the
  encapsulation itself introduced — by decomposition, not by lowering the threshold
- disk storage reads and writes the same canonical 12-key map as the SQL JSON column;
  legacy key names normalized on read, @Expose dropped from domain classes
- 39 settings call sites rewritten across 7 files
- HiddenField backlog cleared (Config, ObstacleGenerator, GhostService, Leaderboard,
  PagedMenu, Reward, ParticleData, World)
- checkstyle ratchet: VisibilityModifier, HiddenField, EmptyLineSeparator and
  MissingDeprecated flipped to error once their counters hit zero; suppressions.xml empty
- javac -Xmaxwarns raised so NullAway/Error Prone counts are honest
  (baseline 165/289, now 164/265)

checkstyle 0 errors / 135 warnings, PMD 0 violations, tests 94/0 fail, ./gradlew check green.
TODO.md: items 30 and 107 updated, new items 167-170, ПРОГРЕСС-6/7 recorded.

src/main/java/dev/loki/loparkour/elytra/obstacle/ObstacleMode.java

@@ -7,6 +7,7 @@ import dev.loki.loparkour.mode.base.ModeMessages;
 import dev.loki.loparkour.player.core.ParkourPlayer;
 import dev.loki.loparkour.session.core.Session;
 import dev.loki.loparkour.util.item.Item;
+import dev.loki.loparkour.player.service.UserRegistry;
 import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -42,8 +43,8 @@ public class ObstacleMode implements Mode {
             return;
         }
 
-        final ParkourPlayer pp = ParkourPlayer.getPlayer(player);
-        if (pp != null && pp.session.generator != null && pp.session.generator.getMode() instanceof ObstacleMode) {
+        final ParkourPlayer pp = UserRegistry.getPlayer(player);
+        if (pp != null && pp.session.generator() != null && pp.session.generator().getMode() instanceof ObstacleMode) {
             return;
         }