feat: Umstellung auf Anthropic Claude SDK, Rechnungsgenerator-Systemtemplate und Task-Status-Sync

- LLM-Integration von LM Studio (Spring AI OpenAI) auf Anthropic Java SDK umgestellt
- Rechnungsgenerator: System-Template für Rechnungen an Nutzer, Canvas leeren, PDF-Vorschau
- Job manuell beenden sendet job_deleted an verbundene App-Clients
- MessageController: nur offene Jobs ausliefern, station_completed per jobId auflösen
- App: Task-Erledigungsstatus aus Server-Tasks auf Stations-Snapshots übernehmen, lokale Task-Status bei Offline-Pufferung erhalten
- Adressbuch-Wording in allen Sprachdateien, Version 0.9.18

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/lib/models/job.dart

@@ -258,6 +258,40 @@ class Job {
       return (a.taskOrder ?? 0).compareTo(b.taskOrder ?? 0);
     }
 
+    // The tasks embedded in deliveryStations are snapshots from job creation
+    // and never reflect later completions. The top-level tasks list comes from
+    // the server's task collection and carries the current completion state,
+    // so overlay it onto the station tasks by id.
+    final topLevelTasksRaw = json['tasks'] ?? jobJson['tasks'];
+    if (deliveryStations.isNotEmpty && topLevelTasksRaw is List) {
+      final freshTasksById = <String, Task>{};
+      for (final rawTask in topLevelTasksRaw) {
+        if (rawTask is! Map) {
+          continue;
+        }
+        try {
+          final task = Task.fromJson(Map<String, dynamic>.from(rawTask));
+          if (task.id.isNotEmpty) {
+            freshTasksById[task.id] = task;
+          }
+        } catch (_) {
+          // Ignore unparseable entries; the station snapshot stays in place.
+        }
+      }
+      for (final station in deliveryStations) {
+        for (var i = 0; i < station.tasks.length; i++) {
+          final fresh = freshTasksById[station.tasks[i].id];
+          if (fresh != null && fresh.completed && !station.tasks[i].completed) {
+            station.tasks[i] = station.tasks[i].copyWith(
+              completed: true,
+              completedAt: fresh.completedAt,
+              completedBy: fresh.completedBy,
+            );
+          }
+        }
+      }
+    }
+
     // Parse tasks array
     List<Task> tasks = [];
     if (deliveryStations.isNotEmpty) {