fix: return UINT32_MAX from findMemType on failure, add [[nodiscard]]

The findMemType/findMemoryType helper in auth_screen, loading_screen,
and vk_context returned 0 on failure — a valid memory type index.
Changed to return UINT32_MAX and log an error, so vkAllocateMemory
receives an invalid index and fails cleanly rather than silently
using the wrong memory type.

Add [[nodiscard]] to VkBuffer::uploadToGPU/createMapped and
VkContext::initialize/recreateSwapchain so callers that ignore
failure are flagged at compile time. Suppress with (void) cast at
3 call sites where failure is non-actionable (resize best-effort).

src/rendering/loading_screen.cpp

@@ -78,7 +78,8 @@ static uint32_t findMemoryType(VkPhysicalDevice physDevice, uint32_t typeFilter,
             return i;
         }
     }
-    return 0;
+    LOG_ERROR("LoadingScreen: no suitable memory type found");
+    return UINT32_MAX;
 }
 
 bool LoadingScreen::loadImage(const std::string& path) {
@@ -420,7 +421,7 @@ void LoadingScreen::render() {
             int w = 0, h = 0;
             SDL_GetWindowSize(sdlWindow, &w, &h);
             if (w > 0 && h > 0) {
-                vkCtx->recreateSwapchain(w, h);
+                (void)vkCtx->recreateSwapchain(w, h);
             }
         }
 

src/rendering/renderer.cpp

@@ -941,7 +941,7 @@ void Renderer::applyMsaaChange() {
     if (!vkCtx->recreateSwapchain(window->getWidth(), window->getHeight())) {
         LOG_ERROR("MSAA change failed — reverting to 1x");
         vkCtx->setMsaaSamples(VK_SAMPLE_COUNT_1_BIT);
-        vkCtx->recreateSwapchain(window->getWidth(), window->getHeight());
+        (void)vkCtx->recreateSwapchain(window->getWidth(), window->getHeight());
     }
 
     // Recreate all sub-renderer pipelines (they embed sample count from render pass)
@@ -1051,7 +1051,7 @@ void Renderer::beginFrame() {
 
     // Handle swapchain recreation if needed
     if (vkCtx->isSwapchainDirty()) {
-        vkCtx->recreateSwapchain(window->getWidth(), window->getHeight());
+        (void)vkCtx->recreateSwapchain(window->getWidth(), window->getHeight());
         // Rebuild water resources that reference swapchain extent/views
         if (waterRenderer) {
             waterRenderer->recreatePipelines();

src/rendering/vk_context.cpp

@@ -1176,7 +1176,8 @@ static uint32_t findMemType(VkPhysicalDevice physDev, uint32_t typeFilter, VkMem
         if ((typeFilter & (1 << i)) && (memProps.memoryTypes[i].propertyFlags & props) == props)
             return i;
     }
-    return 0;
+    LOG_ERROR("VkContext: no suitable memory type found");
+    return UINT32_MAX;
 }
 
 VkDescriptorSet VkContext::uploadImGuiTexture(const uint8_t* rgba, int width, int height) {