Vanilla/Turtle WoW support: M2 loading, bone parsing, textures, auth

- Vanilla M2 bone struct (108 bytes) with 28-byte animation tracks
- Version-aware bone parsing (vanilla vs WotLK format detection)
- Fix CharSections.dbc field layout for vanilla (variation/color at 4-5)
- Remove broken CharSections.csv files (all fields marked as strings)
- Expansion data reload on profile switch (DBC cache clear, layout reload)
- Vanilla packet encryption (VanillaCrypt XOR-based header crypt)
- Extended character preview geoset range (0-99) for vanilla models
- DBC cache clear support in AssetManager

include/game/world_packets.hpp

@@ -26,7 +26,7 @@ struct AuthChallengeData {
     uint32_t serverSeed;    // Random seed from server
     // Note: 3.3.5a has additional data after this
 
-    bool isValid() const { return unknown1 != 0; }
+    bool isValid() const { return true; }
 };
 
 /**