Implements a full character creation UI integrated into the existing flow.
In single-player mode, auth screen now goes to character creation before
entering the world. In online mode, a "Create Character" button on the
character selection screen sends CMSG_CHAR_CREATE to the server. Includes
WoW 3.3.5a race/class combo validation and appearance range limits.
- Add spellbook screen (P key) with Spell.dbc name lookup and action bar assignment
- Default Attack and Hearthstone spells available in single player
- Fix WMO floor clipping (gryphon roost) by tightening ceiling rejection threshold
- Darken ocean water, increase wave motion and opacity
- Add M2 model distance fade-in to prevent pop-in
- Reposition chat window, add slash/enter key focus
- Remove debug key commands (keep only F1 perf HUD, N minimap)
- Performance: return chat history by const ref, use deque for O(1) pop_front
