enhance(mobile): polish UI spacing and background styling in various components

android/app/src/main/java/com/logseq/app/NativeBottomSheetPlugin.kt

@@ -1,6 +1,7 @@
 package com.logseq.app
 
 import android.graphics.Color
+import android.graphics.drawable.GradientDrawable
 import android.os.Handler
 import android.os.Looper
 import android.view.View
@@ -50,9 +51,27 @@ class NativeBottomSheetPlugin : Plugin() {
                 ViewGroup.LayoutParams.MATCH_PARENT
             )
 
+            val cornerRadius = NativeUiUtils.dp(ctx, 16f).toFloat()
+            val roundedBackground = GradientDrawable().apply {
+                setColor(LogseqTheme.current().background)
+                cornerRadii = floatArrayOf(
+                    cornerRadius, cornerRadius,  // 左上角
+                    cornerRadius, cornerRadius,  // 右上角
+                    0f, 0f,                      // 右下角
+                    0f, 0f                       // 左下角
+                )
+            }
+            container!!.background = roundedBackground
+            container!!.clipToOutline = true
+
             val sheet = BottomSheetDialog(ctx)
             sheet.setContentView(container!!)
 
+            sheet.setOnShowListener {
+                val bottomSheet = sheet.findViewById<View>(com.google.android.material.R.id.design_bottom_sheet)
+                bottomSheet?.setBackgroundColor(Color.TRANSPARENT)
+            }
+
             WebViewSnapshotManager.showSnapshot(snapshotTag, webView)
 
             // Move the WebView into the BottomSheet container

android/app/src/main/java/com/logseq/app/NativeSelectionActionBarPlugin.kt

@@ -5,6 +5,7 @@ import android.view.Gravity
 import android.view.View
 import android.view.ViewGroup
 import android.widget.FrameLayout
+import androidx.compose.foundation.BorderStroke
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.horizontalScroll
 import androidx.compose.foundation.layout.Arrangement
@@ -205,8 +206,8 @@ private fun SelectionActionBar(
 
     Surface(
         color = background,
-        shadowElevation = 6.dp,
-        shape = RoundedCornerShape(16.dp)
+        shape = RoundedCornerShape(16.dp),
+        border = BorderStroke(1.dp, tint.copy(alpha = 0.05f))
     ) {
         Row(
             modifier = Modifier