Share the article count line and refresh scaffolding of Today and Learn (review items 5, 6)

articleCountLine, RefreshButton and RefreshableList live in common.dart.
LearnScreen._describe becomes _windowLabel there, and LearnScreen._section
is _kindSection like in SourcesScreen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lib/ui/common.dart

@@ -1,6 +1,9 @@
 import 'package:flutter/material.dart';
 import 'package:url_launcher/url_launcher.dart';
 
+import '../models/source.dart';
+import '../state/app_state.dart';
+
 /// User-facing app name. Platform launcher labels (AndroidManifest, Info.plist,
 /// web/manifest.json, windows/runner) are set separately.
 const appName = 'Tagesbyte';
@@ -33,6 +36,17 @@ const monthNames = [
 bool isSameDay(DateTime a, DateTime b) =>
     a.year == b.year && a.month == b.month && a.day == b.day;
 
+/// The line above the articles of [kind], e.g.
+/// "12 articles · last 24 h · 3 paid/ads hidden".
+String articleCountLine(AppState state, SourceKind kind) {
+  final hidden = state.hiddenCountOf(kind);
+  return '${state.articlesOf(kind).length} articles · last ${_windowLabel(state.windowOf(kind))}'
+      '${hidden > 0 ? ' · $hidden paid/ads hidden' : ''}';
+}
+
+String _windowLabel(Duration window) =>
+    window.inHours < 72 ? '${window.inHours} h' : '${window.inDays} days';
+
 Future<void> openUrl(BuildContext context, String url) async {
   final ok = await launchUrl(Uri.parse(url), mode: LaunchMode.externalApplication);
   if (!ok && context.mounted) {
@@ -41,6 +55,39 @@ Future<void> openUrl(BuildContext context, String url) async {
   }
 }
 
+/// App bar button that refreshes all Sources; off while a refresh runs.
+class RefreshButton extends StatelessWidget {
+  const RefreshButton({super.key, required this.state});
+
+  final AppState state;
+
+  @override
+  Widget build(BuildContext context) => IconButton(
+        tooltip: 'Refresh',
+        onPressed: state.loading ? null : state.refresh,
+        icon: const Icon(Icons.refresh),
+      );
+}
+
+/// A scrollable [list] that refreshes all Sources when pulled down, under a
+/// progress bar while a refresh runs and an optional [notice].
+class RefreshableList extends StatelessWidget {
+  const RefreshableList({super.key, required this.state, required this.list, this.notice});
+
+  final AppState state;
+  final Widget list;
+  final Widget? notice;
+
+  @override
+  Widget build(BuildContext context) => Column(
+        children: [
+          if (state.loading) const LinearProgressIndicator(),
+          if (notice != null) notice!,
+          Expanded(child: RefreshIndicator(onRefresh: state.refresh, child: list)),
+        ],
+      );
+}
+
 /// Centered icon + text + optional action, used for empty and error states.
 class EmptyState extends StatelessWidget {
   const EmptyState({