feat(app): SectionHeader и TileCarousel — общие виджеты редизайна

SectionHeader — заголовок блока с короткой акцентной полоской вместо
разделителя. TileCarousel — горизонтальная прокрутка StatTile вместо
Wrap, не требует общей высоты у детей. Оба без экрана-потребителя пока
не влияют на вид приложения.

app/lib/core/widgets/section_header.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+
+/// A bold section title with a short accent underline beneath its left edge — the
+/// Grimmory-style marker for "a new block starts here" that replaces a divider line.
+/// For a titled card use [SectionCard] instead; this is for a bare block of content
+/// (a chart, a row of tiles, a list) that isn't wrapped in a card of its own.
+class SectionHeader extends StatelessWidget {
+  const SectionHeader({required this.title, this.trailing, super.key});
+
+  final String title;
+  final Widget? trailing;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Row(
+      crossAxisAlignment: CrossAxisAlignment.end,
+      children: [
+        Expanded(
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text(
+                title,
+                style: theme.textTheme.titleLarge?.copyWith(fontWeight: FontWeight.w800),
+              ),
+              const SizedBox(height: 6),
+              Container(
+                width: 28,
+                height: 3,
+                decoration: BoxDecoration(
+                  color: theme.colorScheme.primary,
+                  borderRadius: BorderRadius.circular(2),
+                ),
+              ),
+            ],
+          ),
+        ),
+        ?trailing,
+      ],
+    );
+  }
+}

app/lib/core/widgets/tile_carousel.dart

@@ -0,0 +1,27 @@
+import 'package:flutter/material.dart';
+
+/// A horizontally scrolling row of tiles — the Grimmory-style carousel, used on the
+/// dashboard in place of a [Wrap] of [StatTile]s so a long row of metrics scrolls
+/// instead of wrapping onto a second, uneven line.
+class TileCarousel extends StatelessWidget {
+  const TileCarousel({required this.children, super.key});
+
+  final List<Widget> children;
+
+  @override
+  Widget build(BuildContext context) {
+    return SingleChildScrollView(
+      scrollDirection: Axis.horizontal,
+      child: IntrinsicHeight(
+        child: Row(
+          children: [
+            for (var i = 0; i < children.length; i++) ...[
+              if (i > 0) const SizedBox(width: 12),
+              children[i],
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}