perf: eliminate ~70 unnecessary sqrt ops per frame, optimize caches and threading

Squared distance optimizations across 30 files:
- Convert glm::length() comparisons to glm::dot() (no sqrt)
- Use glm::inversesqrt() for check-then-normalize patterns (1 rsqrt vs 2 sqrt)
- Defer sqrt to after early-out checks in collision/movement code
- Hottest paths: camera_controller (21), weather particles, WMO collision,
  transport movement, creature interpolation, nameplate culling

Container and algorithm improvements:
- std::map<string> → std::unordered_map for asset/DBC/MPQ/warden caches
- std::mutex → std::shared_mutex for asset_manager and mpq_manager caches
- std::sort → std::partial_sort in lighting_manager (top-2 of N volumes)
- Double-lookup find()+operator[] → insert_or_assign in game_handler
- Add reserve() for per-frame vectors: weather, swim_effects, WMO/M2 collision

Threading and synchronization:
- Replace 1ms busy-wait polling with condition_variable in character_renderer
- Move timestamp capture before mutex in logger
- Use memory_order_acquire/release for normal map completion signaling

API additions:
- DBC getStringView()/getStringViewByOffset() for zero-copy string access
- Parse creature display IDs from SMSG_CREATURE_QUERY_SINGLE_RESPONSE

src/rendering/frustum.cpp

@@ -63,10 +63,11 @@ void Frustum::extractFromMatrix(const glm::mat4& vp) {
 }
 
 void Frustum::normalizePlane(Plane& plane) {
-    float length = glm::length(plane.normal);
-    if (length > 0.0001f) {
-        plane.normal /= length;
-        plane.distance /= length;
+    float lenSq = glm::dot(plane.normal, plane.normal);
+    if (lenSq > 0.00000001f) {
+        float invLen = glm::inversesqrt(lenSq);
+        plane.normal *= invLen;
+        plane.distance *= invLen;
     }
 }