Add LLM digest setup and share timestamp context

lib/features/share_intake/domain/share_payload_parser.dart

@@ -1,4 +1,5 @@
 import 'package:relationship_saver/features/local/local_models.dart';
+import 'package:relationship_saver/features/share_intake/domain/shared_message_datetime_extractor.dart';
 import 'package:relationship_saver/features/share_intake/domain/signal_share_parser.dart';
 import 'package:relationship_saver/features/share_intake/whatsapp_share_parser.dart';
 
@@ -20,6 +21,8 @@ class SharePayloadParser {
     final DateTime now = DateTime.now();
     final String normalizedSourceApp = _normalizeSourceApp(sourceApp);
     final String trimmed = rawText.trim();
+    final DateTime? sharedMessageDateTime =
+        SharedMessageDateTimeExtractor.extract(trimmed, now: receivedAt ?? now);
     final _ParsedSourceMetadata? sourceMetadata = _parseSourceMetadata(
       sourceApp: normalizedSourceApp,
       rawText: trimmed,
@@ -48,6 +51,7 @@ class SharePayloadParser {
       url: url,
       createdAt: createdAt ?? now,
       receivedAt: receivedAt ?? now,
+      sharedMessageDateTime: sharedMessageDateTime,
       platform: platform,
       sourceDisplayName: sourceMetadata?.sourceDisplayName,
       sourceUserId: sourceMetadata?.sourceUserId,
@@ -56,11 +60,14 @@ class SharePayloadParser {
         if (normalizedSourceApp != 'share_sheet')
           'source_app_$normalizedSourceApp',
         if (url != null) 'contains_url',
+        if (sharedMessageDateTime != null) 'shared_message_datetime_detected',
         if (sourceMetadata?.sourceDisplayName case final String _)
           'sender_detected',
       ],
       metadata: <String, String>{
         if (url case final String value) 'primaryUrl': value,
+        if (sharedMessageDateTime case final DateTime value)
+          'shared_message_datetime': value.toUtc().toIso8601String(),
       },
     );
   }