fix: resolve all GitHub CodeQL security/quality alerts

Fix 9 integer-multiplication-cast-to-long warnings across 6 files:
- wmo_renderer.cpp: grid cell count and height variance calculation
- composite_renderer.cpp: overlay tile grid allocation
- vk_texture.cpp: image size calculation (width*height*bpp)
- m2_renderer.cpp: collision grid cell allocation
- character_renderer.cpp: normal map buffer and height variance
- world_entry_callback_handler.cpp: tile reserve count

All fixes cast operands to size_t/double before multiplication to
prevent integer overflow when dimensions are large.

src/core/world_entry_callback_handler.cpp

@@ -108,7 +108,7 @@ static void precacheNearbyTiles(rendering::TerrainManager* terrainMgr,
     auto [tileX, tileY] = core::coords::worldToTile(renderPos.x, renderPos.y);
     int side = 2 * radius + 1;
     std::vector<std::pair<int,int>> tiles;
-    tiles.reserve(side * side);
+    tiles.reserve(static_cast<size_t>(side) * static_cast<size_t>(side));
     for (int dy = -radius; dy <= radius; dy++)
         for (int dx = -radius; dx <= radius; dx++)
             tiles.push_back({tileX + dx, tileY + dy});

src/rendering/character_renderer.cpp

@@ -548,7 +548,7 @@ std::unique_ptr<VkTexture> CharacterRenderer::generateNormalHeightMap(
     if (!vkCtx_ || width == 0 || height == 0) return nullptr;
 
     // Use the CPU-only static method, then upload to GPU
-    std::vector<uint8_t> dummy(width * height * 4);
+    std::vector<uint8_t> dummy(static_cast<size_t>(width) * static_cast<size_t>(height) * 4);
     std::memcpy(dummy.data(), pixels, dummy.size());
     auto result = generateNormalHeightMapCPU("", std::move(dummy), width, height);
     outVariance = result.variance;
@@ -585,7 +585,7 @@ CharacterRenderer::NormalMapResult CharacterRenderer::generateNormalHeightMapCPU
         float h = 0.299f * r + 0.587f * g + 0.114f * b;
         heightMap[i] = h;
         sumH += h;
-        sumH2 += h * h;
+        sumH2 += static_cast<double>(h) * static_cast<double>(h);
     }
     double mean = sumH / totalPixels;
     result.variance = static_cast<float>(sumH2 / totalPixels - mean * mean);

src/rendering/m2_renderer.cpp

@@ -1032,8 +1032,8 @@ void M2ModelGPU::CollisionMesh::build() {
     gridCellsX = std::max(1, std::min(32, static_cast<int>(std::ceil((bmax.x - bmin.x) / CELL_SIZE))));
     gridCellsY = std::max(1, std::min(32, static_cast<int>(std::ceil((bmax.y - bmin.y) / CELL_SIZE))));
 
-    cellFloorTris.resize(gridCellsX * gridCellsY);
-    cellWallTris.resize(gridCellsX * gridCellsY);
+    cellFloorTris.resize(static_cast<size_t>(gridCellsX) * static_cast<size_t>(gridCellsY));
+    cellWallTris.resize(static_cast<size_t>(gridCellsX) * static_cast<size_t>(gridCellsY));
     triBounds.resize(triCount);
 
     for (uint32_t ti = 0; ti < triCount; ti++) {

src/rendering/vk_texture.cpp

@@ -49,7 +49,7 @@ bool VkTexture::upload(VkContext& ctx, const uint8_t* pixels, uint32_t width, ui
     else if (format == VK_FORMAT_R8G8_UNORM) bpp = 2;
     else if (format == VK_FORMAT_R8G8B8_UNORM) bpp = 3;
 
-    VkDeviceSize imageSize = width * height * bpp;
+    VkDeviceSize imageSize = static_cast<VkDeviceSize>(width) * static_cast<VkDeviceSize>(height) * bpp;
 
     // Create staging buffer
     AllocatedBuffer staging = createBuffer(ctx.getAllocator(), imageSize,

src/rendering/wmo_renderer.cpp

@@ -2248,7 +2248,7 @@ std::unique_ptr<VkTexture> WMORenderer::generateNormalHeightMap(
         float h = 0.299f * r + 0.587f * g + 0.114f * b;
         heightMap[i] = h;
         sumH += h;
-        sumH2 += h * h;
+        sumH2 += static_cast<double>(h) * static_cast<double>(h);
     }
     double mean = sumH / totalPixels;
     outVariance = static_cast<float>(sumH2 / totalPixels - mean * mean);
@@ -2716,7 +2716,7 @@ void WMORenderer::GroupResources::buildCollisionGrid() {
     if (gridCellsX > 64) gridCellsX = 64;
     if (gridCellsY > 64) gridCellsY = 64;
 
-    size_t totalCells = gridCellsX * gridCellsY;
+    size_t totalCells = static_cast<size_t>(gridCellsX) * static_cast<size_t>(gridCellsY);
     cellTriangles.resize(totalCells);
     cellFloorTriangles.resize(totalCells);
     cellWallTriangles.resize(totalCells);

src/rendering/world_map/composite_renderer.cpp

@@ -30,7 +30,7 @@ void CompositeRenderer::ensureTextureSlots(size_t zoneCount, const std::vector<Z
             slots.overlays.resize(zones[i].overlays.size());
             for (size_t oi = 0; oi < zones[i].overlays.size(); oi++) {
                 const auto& ov = zones[i].overlays[oi];
-                slots.overlays[oi].tiles.resize(ov.tileCols * ov.tileRows, nullptr);
+                slots.overlays[oi].tiles.resize(static_cast<size_t>(ov.tileCols) * static_cast<size_t>(ov.tileRows), nullptr);
             }
         }
     }