Restructure inventory UI, add vendor selling, camera intro on all spawns, and quest log

Split inventory into bags-only (B key) and character screen (C key). Vendor window
auto-opens bags with sell prices on hover and right-click to sell. Add camera intro
pan on all login/spawn/teleport/hearthstone events and idle orbit after 2 minutes.
Add quest log UI, SMSG_MONSTER_MOVE handling, deferred creature spawn queue, and
creature fade-in/movement interpolation for online mode.

include/rendering/character_renderer.hpp

@@ -61,6 +61,9 @@ public:
 
     void setInstancePosition(uint32_t instanceId, const glm::vec3& position);
     void setInstanceRotation(uint32_t instanceId, const glm::vec3& rotation);
+    void moveInstanceTo(uint32_t instanceId, const glm::vec3& destination, float durationSeconds);
+    void startFadeIn(uint32_t instanceId, float durationSeconds);
+    const pipeline::M2Model* getModelData(uint32_t modelId) const;
     void setActiveGeosets(uint32_t instanceId, const std::unordered_set<uint16_t>& geosets);
     void setGroupTextureOverride(uint32_t instanceId, uint16_t geosetGroup, GLuint textureId);
     void setInstanceVisible(uint32_t instanceId, bool visible);
@@ -130,6 +133,18 @@ private:
         // Weapon attachments (weapons parented to this instance's bones)
         std::vector<WeaponAttachment> weaponAttachments;
 
+        // Opacity (for fade-in)
+        float opacity = 1.0f;
+        float fadeInTime = 0.0f;     // elapsed fade time (seconds)
+        float fadeInDuration = 0.0f; // total fade duration (0 = no fade)
+
+        // Movement interpolation
+        bool isMoving = false;
+        glm::vec3 moveStart{0.0f};
+        glm::vec3 moveEnd{0.0f};
+        float moveDuration = 0.0f;   // seconds
+        float moveElapsed = 0.0f;
+
         // Override model matrix (used for weapon instances positioned by parent bone)
         bool hasOverrideModelMatrix = false;
         glm::mat4 overrideModelMatrix{1.0f};