feat: add table_calendar package and CalendarEvent model with tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

test/widget_test.dart

@@ -1,3 +1,4 @@
+import 'package:fabled_app/data/models/calendar_event.dart';
 import 'package:fabled_app/data/api/voice_api.dart';
 import 'package:fabled_app/providers/voice_provider.dart';
 import 'package:fabled_app/data/models/knowledge_item.dart';
@@ -190,6 +191,65 @@ void main() {
     });
   });
 
+  group('CalendarEvent.fromJson', () {
+    test('parses all fields', () {
+      final json = {
+        'id': 10,
+        'title': 'Team meeting',
+        'start_dt': '2026-04-07T09:00:00+00:00',
+        'end_dt': '2026-04-07T10:00:00+00:00',
+        'all_day': false,
+        'description': 'Weekly sync',
+        'location': 'Room 4',
+        'color': '#6366F1',
+        'recurrence': 'FREQ=WEEKLY',
+        'project_id': 3,
+        'reminder_minutes': 15,
+      };
+      final event = CalendarEvent.fromJson(json);
+      expect(event.id, equals(10));
+      expect(event.title, equals('Team meeting'));
+      expect(event.startDt, equals(DateTime.parse('2026-04-07T09:00:00+00:00')));
+      expect(event.endDt, equals(DateTime.parse('2026-04-07T10:00:00+00:00')));
+      expect(event.allDay, isFalse);
+      expect(event.description, equals('Weekly sync'));
+      expect(event.location, equals('Room 4'));
+      expect(event.color, equals('#6366F1'));
+      expect(event.recurrence, equals('FREQ=WEEKLY'));
+      expect(event.projectId, equals(3));
+      expect(event.reminderMinutes, equals(15));
+    });
+
+    test('handles null optional fields', () {
+      final json = {
+        'id': 11,
+        'title': 'Birthday',
+        'start_dt': '2026-05-01T00:00:00+00:00',
+        'end_dt': null,
+        'all_day': true,
+        'description': '',
+        'location': '',
+        'color': '',
+        'recurrence': null,
+        'project_id': null,
+        'reminder_minutes': null,
+      };
+      final event = CalendarEvent.fromJson(json);
+      expect(event.endDt, isNull);
+      expect(event.allDay, isTrue);
+      expect(event.recurrence, isNull);
+      expect(event.projectId, isNull);
+      expect(event.reminderMinutes, isNull);
+    });
+  });
+
+  group('dateOnly', () {
+    test('strips time from datetime', () {
+      final dt = DateTime(2026, 4, 7, 14, 30, 45);
+      expect(dateOnly(dt), equals(DateTime(2026, 4, 7)));
+    });
+  });
+
   group('BriefingFeed.fromJson', () {
     test('parses all fields', () {
       final json = {