feat(UI): add gaussian blur shader core files

package/Shaders/Menu/BackgroundBlurHorizontal.hlsl

@@ -0,0 +1,61 @@
+// Horizontal Blur Pass Shader
+// Part of the BackgroundBlur system - separable Gaussian blur implementation
+
+cbuffer BlurBuffer : register(b0)
+{
+    float4 TexelSize;  // x = 1/width, y = 1/height, z = blur strength, w = unused
+    int4   BlurParams; // x = samples, y = unused, z = unused, w = unused
+};
+
+SamplerState LinearSampler : register(s0);
+Texture2D InputTexture : register(t0);
+
+struct VS_OUTPUT
+{
+    float4 Position : SV_POSITION;
+    float2 TexCoord : TEXCOORD0;
+};
+
+VS_OUTPUT VS_Main(uint vertexID : SV_VertexID)
+{
+    VS_OUTPUT output;
+    output.TexCoord = float2((vertexID << 1) & 2, vertexID & 2);
+    output.Position = float4(output.TexCoord * 2.0f - 1.0f, 0.0f, 1.0f);
+    output.Position.y = -output.Position.y;
+    return output;
+}
+
+// Precomputed normalized Gaussian weights (sigma = 2.0)
+static const float WEIGHTS[8] = {
+    0.1760327f,  // offset 0 (center)
+    0.1658591f,  // offset ±1
+    0.1403215f,  // offset ±2
+    0.1069852f,  // offset ±3
+    0.0732894f,  // offset ±4
+    0.0451904f,  // offset ±5
+    0.0248657f,  // offset ±6
+    0.0122423f   // offset ±7
+};
+
+float4 PS_Main(VS_OUTPUT input) : SV_TARGET
+{
+    const int samples = min(BlurParams.x, 15);
+    const int halfSamples = samples / 2;
+
+    // Sample center pixel
+    float4 result = InputTexture.Sample(LinearSampler, input.TexCoord) * WEIGHTS[0];
+
+    // Sample symmetric pairs (2x loop unrolling opportunity)
+    [unroll(7)]
+    for (int i = 1; i <= halfSamples; ++i)
+    {
+        float weight = WEIGHTS[min(i, 7)];
+        float offset = i * TexelSize.x;
+
+        // Sampler CLAMP mode handles edge cases - no bounds check needed
+        result += InputTexture.Sample(LinearSampler, input.TexCoord + float2(offset, 0.0f)) * weight;
+        result += InputTexture.Sample(LinearSampler, input.TexCoord - float2(offset, 0.0f)) * weight;
+    }
+
+    return result;
+}

package/Shaders/Menu/BackgroundBlurVertical.hlsl

@@ -0,0 +1,61 @@
+// Vertical Blur Pass Shader
+// Part of the BackgroundBlur system - separable Gaussian blur implementation
+
+cbuffer BlurBuffer : register(b0)
+{
+    float4 TexelSize;  // x = 1/width, y = 1/height, z = blur strength, w = unused
+    int4   BlurParams; // x = samples, y = unused, z = unused, w = unused
+};
+
+SamplerState LinearSampler : register(s0);
+Texture2D InputTexture : register(t0);
+
+struct VS_OUTPUT
+{
+    float4 Position : SV_POSITION;
+    float2 TexCoord : TEXCOORD0;
+};
+
+VS_OUTPUT VS_Main(uint vertexID : SV_VertexID)
+{
+    VS_OUTPUT output;
+    output.TexCoord = float2((vertexID << 1) & 2, vertexID & 2);
+    output.Position = float4(output.TexCoord * 2.0f - 1.0f, 0.0f, 1.0f);
+    output.Position.y = -output.Position.y;
+    return output;
+}
+
+// Precomputed normalized Gaussian weights (sigma = 2.0)
+static const float WEIGHTS[8] = {
+    0.1760327f,  // offset 0 (center)
+    0.1658591f,  // offset ±1
+    0.1403215f,  // offset ±2
+    0.1069852f,  // offset ±3
+    0.0732894f,  // offset ±4
+    0.0451904f,  // offset ±5
+    0.0248657f,  // offset ±6
+    0.0122423f   // offset ±7
+};
+
+float4 PS_Main(VS_OUTPUT input) : SV_TARGET
+{
+    const int samples = min(BlurParams.x, 15);
+    const int halfSamples = samples / 2;
+
+    // Sample center pixel
+    float4 result = InputTexture.Sample(LinearSampler, input.TexCoord) * WEIGHTS[0];
+
+    // Sample symmetric pairs (2x loop unrolling opportunity)
+    [unroll(7)]
+    for (int i = 1; i <= halfSamples; ++i)
+    {
+        float weight = WEIGHTS[min(i, 7)];
+        float offset = i * TexelSize.y;
+
+        // Sampler CLAMP mode handles edge cases - no bounds check needed
+        result += InputTexture.Sample(LinearSampler, input.TexCoord + float2(0.0f, offset)) * weight;
+        result += InputTexture.Sample(LinearSampler, input.TexCoord - float2(0.0f, offset)) * weight;
+    }
+
+    return result;
+}