feat(mobile): Pulse polish — flat feed, compose page, shared filter chips, like + accent fixes (#796)

Signed-off-by: Wes <wesbillman@users.noreply.github.com>
Co-authored-by: Brain <21994759fc7a6fa6b965551d35cfd7897d262f2495467f2d78694ddcfa6a5c7e@sprout-oss.stage.blox.sqprod.co>

mobile/test/shared/widgets/filter_chip_bar_test.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sprout_mobile/shared/theme/theme.dart';
+import 'package:sprout_mobile/shared/widgets/filter_chip_bar.dart';
+
+void main() {
+  testWidgets('selected chip resolves the accent (scheme.primary) as fill', (
+    tester,
+  ) async {
+    final accented = applyAccent(darkColorScheme, 0); // Blue accent
+    final accent = accented.primary;
+
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: AppTheme.dark(colorScheme: accented),
+        home: Scaffold(
+          body: FilterChipBar<int>(
+            selected: 0,
+            onSelected: (_) {},
+            items: const [
+              FilterChipItem(id: 0, label: 'Everyone'),
+              FilterChipItem(id: 1, label: 'Following'),
+            ],
+          ),
+        ),
+      ),
+    );
+    await tester.pumpAndSettle();
+
+    // The chip's container color comes from ChipThemeData.color resolved for
+    // the selected state. Resolve it the same way the chip does and assert
+    // it's the accent.
+    final chipTheme = ChipTheme.of(
+      tester.element(find.widgetWithText(RawChip, 'Everyone')),
+    );
+    final resolved = chipTheme.color?.resolve({WidgetState.selected});
+    expect(resolved, accent);
+  });
+}