Fix critical bugs and improve code quality

Generator & Modes:
- Fix potential NPE in ParkourGenerator zone initialization
- Add null check in BlockPlacer.placeNormalBlock()
- Fix unsafe Map operations in CoopMode.score()
- Add session validation in RaceMode delayed reset
- Extract magic number to constant in SpeedrunMode (TICKS_PER_SECOND)
- Add world bounds checking in ElytraRingGenerator
- Fix map normalization in GeneratorProfileManager (handle zero sum)
- Complete schematic implementation in BlockPlacer

Storage & Database:
- CRITICAL: Fix connection leak in SQLConnectionManager
- Add proper try-with-resources for Connection in SQLQueryExecutor
- Deprecate unsafe prepareStatement() method
- Add documentation about connection management

Session & Player:
- Optimize muted users count calculation in SessionStateManager

All changes tested and verified with build + tests passing.

src/main/java/dev/loki/loparkour/session/SessionStateManager.java

@@ -93,7 +93,7 @@ public class SessionStateManager {
      * Get muted users count.
      */
     public int getMutedUsersCount() {
-        return (int) mutedUsers.values().stream().mapToInt(muted -> muted ? 1 : 0).sum();
+        return (int) mutedUsers.values().stream().filter(muted -> muted).count();
     }
     
     /**