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/renderer.hpp

@@ -123,6 +123,10 @@ public:
     bool isMoving() const;
     void triggerMeleeSwing();
 
+    // Selection circle for targeted entity
+    void setSelectionCircle(const glm::vec3& pos, float radius, const glm::vec3& color);
+    void clearSelectionCircle();
+
     // CPU timing stats (milliseconds, last frame).
     double getLastUpdateMs() const { return lastUpdateMs; }
     double getLastRenderMs() const { return lastRenderMs; }
@@ -224,6 +228,18 @@ private:
     // Target facing
     const glm::vec3* targetPosition = nullptr;
 
+    // Selection circle rendering
+    uint32_t selCircleVAO = 0;
+    uint32_t selCircleVBO = 0;
+    uint32_t selCircleShader = 0;
+    int selCircleVertCount = 0;
+    void initSelectionCircle();
+    void renderSelectionCircle(const glm::mat4& view, const glm::mat4& projection);
+    glm::vec3 selCirclePos{0.0f};
+    glm::vec3 selCircleColor{1.0f, 0.0f, 0.0f};
+    float selCircleRadius = 1.5f;
+    bool selCircleVisible = false;
+
     // Footstep event tracking (animation-driven)
     uint32_t footstepLastAnimationId = 0;
     float footstepLastNormTime = 0.0f;