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/charge_effect.cpp

@@ -449,8 +449,9 @@ void ChargeEffect::emit(const glm::vec3& position, const glm::vec3& direction) {
     }
 
     // Only add a new trail point if we've moved enough
-    float dist = glm::length(position - lastEmitPos_);
-    if (dist >= TRAIL_SPAWN_DIST || trail_.empty()) {
+    glm::vec3 emitDelta = position - lastEmitPos_;
+    float distSq = glm::dot(emitDelta, emitDelta);
+    if (distSq >= TRAIL_SPAWN_DIST * TRAIL_SPAWN_DIST || trail_.empty()) {
         // Ribbon is vertical: side vector points straight up
         glm::vec3 side = glm::vec3(0.0f, 0.0f, 1.0f);
 
@@ -466,9 +467,10 @@ void ChargeEffect::emit(const glm::vec3& position, const glm::vec3& direction) {
 
     // Spawn dust puffs at feet
     glm::vec3 horizDir = glm::vec3(direction.x, direction.y, 0.0f);
-    float horizLen = glm::length(horizDir);
-    if (horizLen < 0.001f) return;
-    glm::vec3 backDir = -horizDir / horizLen;
+    float horizLenSq = glm::dot(horizDir, horizDir);
+    if (horizLenSq < 1e-6f) return;
+    float invHorizLen = glm::inversesqrt(horizLenSq);
+    glm::vec3 backDir = -horizDir * invHorizLen;
     glm::vec3 sideDir = glm::vec3(-backDir.y, backDir.x, 0.0f);
 
     dustAccum_ += 30.0f * 0.016f;