feat: add brightness slider to Video settings

Black overlay dims below 50%, white overlay brightens above 50%.
Persisted in settings.cfg, with restore-defaults support.

include/rendering/renderer.hpp

@@ -381,6 +381,13 @@ private:
     void initOverlayPipeline();
     void renderOverlay(const glm::vec4& color, VkCommandBuffer overrideCmd = VK_NULL_HANDLE);
 
+    // Brightness (1.0 = default, <1 darkens, >1 brightens)
+    float brightness_ = 1.0f;
+public:
+    void setBrightness(float b) { brightness_ = b; }
+    float getBrightness() const { return brightness_; }
+private:
+
     // FSR 1.0 upscaling state
     struct FSRState {
         bool enabled = false;

include/ui/game_screen.hpp

@@ -171,6 +171,7 @@ private:
     bool pendingShadows = true;
     float pendingShadowDistance = 300.0f;
     bool pendingWaterRefraction = false;
+    int pendingBrightness = 50; // 0-100, maps to 0.0-2.0 (50 = 1.0 default)
     int pendingMasterVolume = 100;
     int pendingMusicVolume = 30;
     int pendingAmbientVolume = 100;

src/rendering/renderer.cpp

@@ -5287,6 +5287,13 @@ void Renderer::renderWorld(game::World* world, game::GameHandler* gameHandler) {
                     renderOverlay(tint, cmd);
                 }
             }
+            // Brightness overlay (applied before minimap so it doesn't affect UI)
+            if (brightness_ < 0.99f) {
+                renderOverlay(glm::vec4(0.0f, 0.0f, 0.0f, 1.0f - brightness_), cmd);
+            } else if (brightness_ > 1.01f) {
+                float alpha = (brightness_ - 1.0f) / 1.0f; // maps 1.0-2.0 → 0.0-1.0
+                renderOverlay(glm::vec4(1.0f, 1.0f, 1.0f, alpha), cmd);
+            }
             if (minimap && minimap->isEnabled() && camera && window) {
                 glm::vec3 minimapCenter = camera->getPosition();
                 if (cameraController && cameraController->isThirdPerson())
@@ -5421,6 +5428,13 @@ void Renderer::renderWorld(game::World* world, game::GameHandler* gameHandler) {
                 renderOverlay(tint);
             }
         }
+        // Brightness overlay (applied before minimap so it doesn't affect UI)
+        if (brightness_ < 0.99f) {
+            renderOverlay(glm::vec4(0.0f, 0.0f, 0.0f, 1.0f - brightness_));
+        } else if (brightness_ > 1.01f) {
+            float alpha = (brightness_ - 1.0f) / 1.0f;
+            renderOverlay(glm::vec4(1.0f, 1.0f, 1.0f, alpha));
+        }
         if (minimap && minimap->isEnabled() && camera && window) {
             glm::vec3 minimapCenter = camera->getPosition();
             if (cameraController && cameraController->isThirdPerson())

src/ui/game_screen.cpp

@@ -14900,6 +14900,16 @@ void GameScreen::renderSettingsWindow() {
                 ImGui::Separator();
                 ImGui::Spacing();
 
+                ImGui::SetNextItemWidth(200.0f);
+                if (ImGui::SliderInt("Brightness", &pendingBrightness, 0, 100, "%d%%")) {
+                    if (renderer) renderer->setBrightness(static_cast<float>(pendingBrightness) / 50.0f);
+                    saveSettings();
+                }
+
+                ImGui::Spacing();
+                ImGui::Separator();
+                ImGui::Spacing();
+
                 if (ImGui::Button("Restore Video Defaults", ImVec2(-1, 0))) {
                     pendingFullscreen = kDefaultFullscreen;
                     pendingVsync = kDefaultVsync;
@@ -14912,9 +14922,11 @@ void GameScreen::renderSettingsWindow() {
                     pendingPOM = true;
                     pendingPOMQuality = 1;
                     pendingResIndex = defaultResIndex;
+                    pendingBrightness = 50;
                     window->setFullscreen(pendingFullscreen);
                     window->setVsync(pendingVsync);
                     window->applyResolution(kResolutions[pendingResIndex][0], kResolutions[pendingResIndex][1]);
+                    if (renderer) renderer->setBrightness(1.0f);
                     pendingWaterRefraction = false;
                     if (renderer) {
                         renderer->setShadowsEnabled(pendingShadows);
@@ -17284,6 +17296,7 @@ void GameScreen::saveSettings() {
     out << "ground_clutter_density=" << pendingGroundClutterDensity << "\n";
     out << "shadows=" << (pendingShadows ? 1 : 0) << "\n";
     out << "shadow_distance=" << pendingShadowDistance << "\n";
+    out << "brightness=" << pendingBrightness << "\n";
     out << "water_refraction=" << (pendingWaterRefraction ? 1 : 0) << "\n";
     out << "antialiasing=" << pendingAntiAliasing << "\n";
     out << "fxaa=" << (pendingFXAA ? 1 : 0) << "\n";
@@ -17428,6 +17441,11 @@ void GameScreen::loadSettings() {
             else if (key == "ground_clutter_density") pendingGroundClutterDensity = std::clamp(std::stoi(val), 0, 150);
             else if (key == "shadows") pendingShadows = (std::stoi(val) != 0);
             else if (key == "shadow_distance") pendingShadowDistance = std::clamp(std::stof(val), 40.0f, 500.0f);
+            else if (key == "brightness") {
+                pendingBrightness = std::clamp(std::stoi(val), 0, 100);
+                if (auto* r = core::Application::getInstance().getRenderer())
+                    r->setBrightness(static_cast<float>(pendingBrightness) / 50.0f);
+            }
             else if (key == "water_refraction") pendingWaterRefraction = (std::stoi(val) != 0);
             else if (key == "antialiasing") pendingAntiAliasing = std::clamp(std::stoi(val), 0, 3);
             else if (key == "fxaa") pendingFXAA = (std::stoi(val) != 0);