Initial commit: Tagesbyte prototype

Flutter app that collects daily tech news from German and English RSS/Atom
feeds, with a reader view, AI article summaries and daily briefings (Claude
API or n8n webhook), paywall/sponsored filtering and ad/consent blocking.

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

lib/services/summarizer.dart

@@ -0,0 +1,88 @@
+import '../models/article.dart';
+import '../models/briefing.dart';
+import '../models/news_source.dart';
+
+class SummarizerException implements Exception {
+  SummarizerException(this.message);
+
+  final String message;
+
+  @override
+  String toString() => message;
+}
+
+/// Something that can turn articles into summaries. Implemented by the
+/// direct Claude API client and by the n8n webhook bridge.
+abstract class Summarizer {
+  String get name;
+
+  Future<String> summarizeArticle(Article article, String text, SourceLanguage language);
+
+  Future<DailyBriefing> createBriefing(List<Article> articles, SourceLanguage language);
+}
+
+/// Shared prompt material and response mapping for all summarizers.
+class BriefingInput {
+  BriefingInput(List<Article> articles)
+      : byId = {for (var i = 0; i < articles.length; i++) 'a${i + 1}': articles[i]};
+
+  /// Short ids keep the prompt compact and are easy for the model to cite.
+  final Map<String, Article> byId;
+
+  static const excerptChars = 220;
+
+  String toPromptList() {
+    final buffer = StringBuffer();
+    byId.forEach((id, a) {
+      final excerpt = a.excerpt.length > excerptChars
+          ? '${a.excerpt.substring(0, excerptChars)}…'
+          : a.excerpt;
+      buffer.writeln('[$id] (${a.source.name}) ${a.title}'
+          '${excerpt.isEmpty ? '' : ' — $excerpt'}');
+    });
+    return buffer.toString();
+  }
+
+  List<Map<String, dynamic>> toJsonList() => [
+        for (final e in byId.entries)
+          {
+            'id': e.key,
+            'title': e.value.title,
+            'url': e.value.link,
+            'source': e.value.source.name,
+            'language': e.value.source.language.name,
+            'published': e.value.published?.toIso8601String(),
+            'excerpt': e.value.excerpt,
+          }
+      ];
+
+  /// Maps `{intro, topics: [{title, summary, article_ids}]}` onto a briefing.
+  DailyBriefing toBriefing(Map<String, dynamic> json, String generatedBy) {
+    final topics = (json['topics'] as List? ?? []).map((t) {
+      final topic = t as Map<String, dynamic>;
+      final ids = (topic['article_ids'] as List? ?? []).cast<String>();
+      return BriefingTopic(
+        title: topic['title'] as String? ?? '',
+        summary: topic['summary'] as String? ?? '',
+        sources: [
+          for (final id in ids)
+            if (byId[id] != null)
+              ArticleRef(
+                title: byId[id]!.title,
+                url: byId[id]!.link,
+                sourceName: byId[id]!.source.name,
+              ),
+        ],
+      );
+    }).toList();
+    return DailyBriefing(
+      createdAt: DateTime.now(),
+      intro: json['intro'] as String? ?? '',
+      topics: topics,
+      generatedBy: generatedBy,
+    );
+  }
+}
+
+String languageName(SourceLanguage language) =>
+    language == SourceLanguage.de ? 'German' : 'English';