Add WoW-style camera system with collision and first-person mode

- Implement orbit camera with smooth zoom and collision detection
- Add 50° slope limiting with sliding (prevents mountain climbing)
- Add first-person mode that hides player model and weapons
- Add floor clearance check to prevent camera clipping through ground
- Improve WMO wall collision with proper height range checks
- Add two-sided floor collision detection for WMO geometry
- Increase M2 render distance slightly for better visibility

include/rendering/character_renderer.hpp

@@ -61,6 +61,7 @@ public:
     void setInstancePosition(uint32_t instanceId, const glm::vec3& position);
     void setInstanceRotation(uint32_t instanceId, const glm::vec3& rotation);
     void setActiveGeosets(uint32_t instanceId, const std::unordered_set<uint16_t>& geosets);
+    void setInstanceVisible(uint32_t instanceId, bool visible);
     void removeInstance(uint32_t instanceId);
 
     /** Attach a weapon model to a character instance at the given attachment point. */
@@ -95,6 +96,7 @@ private:
         glm::vec3 position;
         glm::vec3 rotation;
         float scale;
+        bool visible = true;  // For first-person camera hiding
 
         // Animation state
         uint32_t currentAnimationId = 0;