feat: Add spawn position caching and spiral scan optimization (#2295)

### Summary

Adds spawn position caching and optimization for constrained spawners (e.g., those near houses, water, or blocked terrain).

### Key features:
- Sector-based bitmap cache (32 bytes per 16x16 sector) stores valid spawn positions
- Spiral scan progressively discovers positions from spawner center outward
- Automatic mode detects constrained spawners after 5+ non-transient failures
- Prevents mob spawning inside private houses (allows public AoS buildings)
- Deduplicates sector lookups for multi-bounds spawners (RegionSpawner)
- Cache invalidation on house placement/demolition
- Moves SpawnBounds to Spawner

### New spawner properties:
- SpawnPositionMode: Automatic (default), Enabled, Disabled, Abandoned
- MaxSpawnAttempts: Configurable attempts before optimization engages (default: 5)

Projects/UOContent/Multis/Houses/BaseHouse.cs

@@ -4,6 +4,7 @@ using ModernUO.CodeGeneratedEvents;
 using Server.Accounting;
 using Server.Collections;
 using Server.ContextMenus;
+using Server.Engines.Spawners;
 using Server.Ethics;
 using Server.Guilds;
 using Server.Gumps;
@@ -1561,6 +1562,19 @@ namespace Server.Multis
 
             UpdateRegion();
 
+            // Invalidate spawn position cache for affected sectors
+            if (Map != null && Map != Map.Internal)
+            {
+                var mcl = Components;
+                var bounds = new Rectangle2D(
+                    X + mcl.Min.X,
+                    Y + mcl.Min.Y,
+                    mcl.Width,
+                    mcl.Height
+                );
+                SectorSpawnCacheManager.InvalidateSectors(Map, bounds);
+            }
+
             if (Sign?.Deleted == false)
             {
                 Sign.Map = Map;
@@ -3329,6 +3343,19 @@ namespace Server.Multis
         {
             RestoreRelocatedEntities();
 
+            // Invalidate spawn position cache for affected sectors before deletion
+            if (Map != null && Map != Map.Internal)
+            {
+                var mcl = Components;
+                var bounds = new Rectangle2D(
+                    X + mcl.Min.X,
+                    Y + mcl.Min.Y,
+                    mcl.Width,
+                    mcl.Height
+                );
+                SectorSpawnCacheManager.InvalidateSectors(Map, bounds);
+            }
+
             new FixColumnTimer(this).Start();
 
             base.OnDelete();