Skyllia

Add per-island build height limits

• Add islands_build_height table (MariaDB, PostgreSQL, SQLite)
• Add IslandBuildHeightQuery abstract class and 3 implementations
• Add HeightType enum (MIN/MAX)
• Extend Island API with getBuildMinHeight, getBuildMaxHeight, setBuildHeight
• Cache height values in IslandHook to avoid per-event DB queries
• Enforce height limits in ListenersUtils.isBlockOutsideIsland (Y-axis check)
• Add /isadmin setheight <min|max> confirm command
• Support optional min-build-height/max-build-height in schematics.toml
• Apply schematic height config on island creation