feat(epub): overhaul border system to support individual sides and radii (#44)

- Refactored `BlockStyle` to replace unified border/radius fields with explicit properties for all four sides and corners.
- Overhauled `CssParser` to correctly handle CSS border shorthands (`border-bottom`, `border-width`, etc.) and multi-value `border-radius`.
- Implemented `drawCssBorders` custom modifier to render side-specific borders, styles (dashed/dotted), and background clipping.
- Updated `Paginator` measurement logic to calculate block height and splitting points based on individual side widths.

app/src/main/java/com/aryan/reader/paginatedreader/PaginatedReaderData.kt

@@ -51,28 +51,34 @@ data class BlockStyle(
     @ProtoNumber(4) @Serializable(with = DpSerializer::class) val maxWidth: Dp = Dp.Unspecified,
     @ProtoNumber(5) @Serializable(with = DpSerializer::class) val height: Dp = Dp.Unspecified,
     @ProtoNumber(6) @Serializable(with = ColorSerializer::class) val backgroundColor: Color = Color.Unspecified,
-    @ProtoNumber(7) val border: BorderStyle? = null,
-    @ProtoNumber(8) val listStyleType: String? = null,
-    @ProtoNumber(9) val listStyleImage: String? = null,
-    @ProtoNumber(10) val pageBreakInsideAvoid: Boolean = false,
-    @ProtoNumber(11) val pageBreakAfterAvoid: Boolean = false,
-    @ProtoNumber(12) val boxSizing: String? = null,
-    @ProtoNumber(13) val float: String? = null,
-    @ProtoNumber(14) val clear: String? = null,
-    @ProtoNumber(15) val position: String? = null,
-    @ProtoNumber(16) @Serializable(with = DpSerializer::class) val top: Dp = Dp.Unspecified,
-    @ProtoNumber(17) @Serializable(with = DpSerializer::class) val right: Dp = Dp.Unspecified,
-    @ProtoNumber(18) @Serializable(with = DpSerializer::class) val bottom: Dp = Dp.Unspecified,
-    @ProtoNumber(19) @Serializable(with = DpSerializer::class) val left: Dp = Dp.Unspecified,
-    @ProtoNumber(20) val display: String? = null,
-    @ProtoNumber(21) val flexDirection: String? = null,
-    @ProtoNumber(22) val justifyContent: String? = null,
-    @ProtoNumber(23) val alignItems: String? = null,
-    @ProtoNumber(24) val horizontalAlign: String? = null,
-    @ProtoNumber(25) val filter: String? = null,
-    @ProtoNumber(26) val borderCollapse: String? = null,
-    @ProtoNumber(27) @Serializable(with = DpSerializer::class) val borderSpacing: Dp = 0.dp,
-    @ProtoNumber(28) @Serializable(with = DpSerializer::class) val borderRadius: Dp = 0.dp
+    @ProtoNumber(7) val borderTop: BorderStyle? = null,
+    @ProtoNumber(8) val borderRight: BorderStyle? = null,
+    @ProtoNumber(9) val borderBottom: BorderStyle? = null,
+    @ProtoNumber(10) val borderLeft: BorderStyle? = null,
+    @ProtoNumber(11) val listStyleType: String? = null,
+    @ProtoNumber(12) val listStyleImage: String? = null,
+    @ProtoNumber(13) val pageBreakInsideAvoid: Boolean = false,
+    @ProtoNumber(14) val pageBreakAfterAvoid: Boolean = false,
+    @ProtoNumber(15) val boxSizing: String? = null,
+    @ProtoNumber(16) val float: String? = null,
+    @ProtoNumber(17) val clear: String? = null,
+    @ProtoNumber(18) val position: String? = null,
+    @ProtoNumber(19) @Serializable(with = DpSerializer::class) val top: Dp = Dp.Unspecified,
+    @ProtoNumber(20) @Serializable(with = DpSerializer::class) val right: Dp = Dp.Unspecified,
+    @ProtoNumber(21) @Serializable(with = DpSerializer::class) val bottom: Dp = Dp.Unspecified,
+    @ProtoNumber(22) @Serializable(with = DpSerializer::class) val left: Dp = Dp.Unspecified,
+    @ProtoNumber(23) val display: String? = null,
+    @ProtoNumber(24) val flexDirection: String? = null,
+    @ProtoNumber(25) val justifyContent: String? = null,
+    @ProtoNumber(26) val alignItems: String? = null,
+    @ProtoNumber(27) val horizontalAlign: String? = null,
+    @ProtoNumber(28) val filter: String? = null,
+    @ProtoNumber(29) val borderCollapse: String? = null,
+    @ProtoNumber(30) @Serializable(with = DpSerializer::class) val borderTopLeftRadius: Dp = 0.dp,
+    @ProtoNumber(31) @Serializable(with = DpSerializer::class) val borderTopRightRadius: Dp = 0.dp,
+    @ProtoNumber(32) @Serializable(with = DpSerializer::class) val borderBottomRightRadius: Dp = 0.dp,
+    @ProtoNumber(33) @Serializable(with = DpSerializer::class) val borderBottomLeftRadius: Dp = 0.dp,
+    @ProtoNumber(34) @Serializable(with = DpSerializer::class) val borderSpacing: Dp = 0.dp
 ) {
     fun merge(other: BlockStyle): BlockStyle {
         return BlockStyle(
@@ -92,7 +98,14 @@ data class BlockStyle(
             maxWidth = if (other.maxWidth != Dp.Unspecified) other.maxWidth else this.maxWidth,
             height = if (other.height != Dp.Unspecified) other.height else this.height,
             backgroundColor = if (other.backgroundColor.isSpecified) other.backgroundColor else this.backgroundColor,
-            border = other.border ?: this.border,
+            borderTop = other.borderTop ?: this.borderTop,
+            borderRight = other.borderRight ?: this.borderRight,
+            borderBottom = other.borderBottom ?: this.borderBottom,
+            borderLeft = other.borderLeft ?: this.borderLeft,
+            borderTopLeftRadius = if (other.borderTopLeftRadius != 0.dp) other.borderTopLeftRadius else this.borderTopLeftRadius,
+            borderTopRightRadius = if (other.borderTopRightRadius != 0.dp) other.borderTopRightRadius else this.borderTopRightRadius,
+            borderBottomRightRadius = if (other.borderBottomRightRadius != 0.dp) other.borderBottomRightRadius else this.borderBottomRightRadius,
+            borderBottomLeftRadius = if (other.borderBottomLeftRadius != 0.dp) other.borderBottomLeftRadius else this.borderBottomLeftRadius,
             listStyleType = other.listStyleType ?: this.listStyleType,
             listStyleImage = other.listStyleImage ?: this.listStyleImage,
             pageBreakInsideAvoid = this.pageBreakInsideAvoid || other.pageBreakInsideAvoid,
@@ -112,8 +125,7 @@ data class BlockStyle(
             horizontalAlign = other.horizontalAlign ?: this.horizontalAlign,
             filter = other.filter ?: this.filter,
             borderCollapse = other.borderCollapse ?: this.borderCollapse,
-            borderSpacing = if (other.borderSpacing != 0.dp) other.borderSpacing else this.borderSpacing,
-            borderRadius = if (other.borderRadius != 0.dp) other.borderRadius else this.borderRadius
+            borderSpacing = if (other.borderSpacing != 0.dp) other.borderSpacing else this.borderSpacing
         )
     }
 }