fix(home): 重绘二级筛选三线图标

lib/core/theme/app_colors.dart

@@ -81,6 +81,7 @@ abstract final class AppColors {
   static const textSecondary = Color(0xFF8E8E93);
   static const textTertiary = Color(0xFF9E9E9E);
   static const textTabInactive = Color(0xFFB0B0B0);
+  static const textFilterIcon = Color(0xFF7A7A7E);
 
   /// 原生开屏与冷启动过渡底色。
   static const splashInk = ink;

lib/core/theme/app_dimens.dart

@@ -113,7 +113,8 @@ abstract final class AppDimens {
   static const double homeSecondaryTagRadius = 13;
   static const double homeSecondaryFilterGap = 8;
   static const double homeSecondaryFilterVisualSize = 26;
-  static const double homeSecondaryFilterIcon = 18;
+  static const double homeSecondaryFilterIcon = 16;
+  static const double homeSecondaryFilterStroke = 1.7;
   static const double homePrimaryCategoryGap = 24;
   static const double homeSecondaryTagGap = 14;
   static const double homeSearchTopGap = 0;

lib/pages/home/widgets/home_grid_header.dart

@@ -342,10 +342,12 @@ class HomeGridHeader extends StatelessWidget {
                   child: Center(
                     child: SizedBox.square(
                       dimension: AppDimens.homeSecondaryFilterVisualSize,
-                      child: const Icon(
-                        Icons.filter_list_rounded,
-                        color: AppColors.textTertiary,
-                        size: AppDimens.homeSecondaryFilterIcon,
+                      child: const Center(
+                        child: CustomPaint(
+                          key: Key('home-secondary-filter-icon'),
+                          size: Size.square(AppDimens.homeSecondaryFilterIcon),
+                          painter: _ThreeLineFilterPainter(),
+                        ),
                       ),
                     ),
                   ),
@@ -395,3 +397,26 @@ class HomeGridHeader extends StatelessWidget {
     );
   }
 }
+
+class _ThreeLineFilterPainter extends CustomPainter {
+  const _ThreeLineFilterPainter();
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    final paint = Paint()
+      ..color = AppColors.textFilterIcon
+      ..strokeWidth = AppDimens.homeSecondaryFilterStroke
+      ..strokeCap = StrokeCap.butt;
+    final positions = [
+      size.height * 0.25,
+      size.height * 0.5,
+      size.height * 0.75,
+    ];
+    for (final y in positions) {
+      canvas.drawLine(Offset(0, y), Offset(size.width, y), paint);
+    }
+  }
+
+  @override
+  bool shouldRepaint(_ThreeLineFilterPainter oldDelegate) => false;
+}