Fix character geoset mapping and texture corruption on equipment change

Corrected CharGeosets group assignments verified via vertex bounding boxes:
- Group 4 (401+) = gloves/forearms, Group 5 (501+) = boots/shins,
  Group 8 (801+) = sleeves (chest-controlled), Group 9 = kneepads,
  Group 13 (1301+) = pants/trousers, Group 20 (2002) = bare feet
- Changed bare shin default from 501 to 502 for better width match
  with thigh mesh (0.39 vs 0.32, thighs are 0.42)
- Added clearCompositeCache() to prevent stale composite textures
  from being reused across equipment changes
- Fixed character preview geoset defaults to match corrected mapping

Data/expansions/wotlk/dbc_layouts.json

@@ -12,8 +12,9 @@
   },
   "CharSections": {
     "RaceID": 1, "SexID": 2, "BaseSection": 3,
-    "Texture1": 4, "Texture2": 5, "Texture3": 6,
-    "Flags": 7, "VariationIndex": 8, "ColorIndex": 9
+    "VariationIndex": 4, "ColorIndex": 5,
+    "Texture1": 6, "Texture2": 7, "Texture3": 8,
+    "Flags": 9
   },
   "SpellIcon": { "ID": 0, "Path": 1 },
   "FactionTemplate": {