style: add GradientBorderCardView with theme-aware gradient border implementation

src/android/app/src/main/java/org/yuzu/yuzu_emu/views/GradientBorderCardView.kt

@@ -0,0 +1,120 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// SPDX-FileCopyrightText: 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+package org.yuzu.yuzu_emu.views
+
+import android.content.Context
+import android.graphics.*
+import android.util.AttributeSet
+import com.google.android.material.card.MaterialCardView
+import org.yuzu.yuzu_emu.R
+import org.yuzu.yuzu_emu.features.settings.model.Settings
+import androidx.preference.PreferenceManager
+
+class GradientBorderCardView @JvmOverloads constructor(
+    context: Context,
+    attrs: AttributeSet? = null,
+    defStyleAttr: Int = 0
+) : MaterialCardView(context, attrs, defStyleAttr) {
+
+    private val borderPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
+        style = Paint.Style.STROKE
+        strokeWidth = 6f
+    }
+
+    private val borderPath = Path()
+    private val borderRect = RectF()
+    private var showGradientBorder = false
+    private var isEdenTheme = false
+
+    init {
+        setWillNotDraw(false)
+        updateThemeState()
+    }
+
+    private fun updateThemeState() {
+        val prefs = PreferenceManager.getDefaultSharedPreferences(context)
+        val themeIndex = try {
+            prefs.getInt(Settings.PREF_STATIC_THEME_COLOR, 0)
+        } catch (e: Exception) {
+            0 // Default to Eden theme if error
+        }
+        isEdenTheme = themeIndex == 0
+    }
+
+    override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
+        super.onSizeChanged(w, h, oldw, oldh)
+
+        // Update border style based on theme
+        if (isEdenTheme) {
+            // Gradient for Eden theme
+            borderPaint.shader = LinearGradient(
+                0f, 0f,
+                w.toFloat(), h.toFloat(),
+                context.getColor(R.color.eden_border_gradient_start),
+                context.getColor(R.color.eden_border_gradient_end),
+                Shader.TileMode.CLAMP
+            )
+        } else {
+            // Solid color for other themes
+            borderPaint.shader = null
+            val typedValue = android.util.TypedValue()
+            context.theme.resolveAttribute(com.google.android.material.R.attr.colorPrimary, typedValue, true)
+            borderPaint.color = typedValue.data
+        }
+
+        // Update border rect with padding for stroke
+        val halfStroke = borderPaint.strokeWidth / 2
+        borderRect.set(
+            halfStroke,
+            halfStroke,
+            w - halfStroke,
+            h - halfStroke
+        )
+
+        // Update path with rounded corners
+        borderPath.reset()
+        borderPath.addRoundRect(
+            borderRect,
+            radius,
+            radius,
+            Path.Direction.CW
+        )
+    }
+
+    override fun onFocusChanged(gainFocus: Boolean, direction: Int, previouslyFocusedRect: Rect?) {
+        super.onFocusChanged(gainFocus, direction, previouslyFocusedRect)
+        showGradientBorder = gainFocus
+        invalidate()
+    }
+
+    override fun setSelected(selected: Boolean) {
+        super.setSelected(selected)
+        showGradientBorder = selected
+        invalidate()
+    }
+
+    override fun setPressed(pressed: Boolean) {
+        super.setPressed(pressed)
+        if (pressed) {
+            showGradientBorder = true
+            invalidate()
+        }
+    }
+
+    override fun onDraw(canvas: Canvas) {
+        super.onDraw(canvas)
+        if (showGradientBorder && !isPressed) {
+            canvas.drawPath(borderPath, borderPaint)
+        }
+    }
+
+    override fun onAttachedToWindow() {
+        super.onAttachedToWindow()
+        updateThemeState()
+        requestLayout()
+    }
+}