feat: add local-first private AI digest workflow

Migrate app code into canonical feature slices, add phone-only AI digest scheduling and review, wire local notification/background task support, and cover the flow with tests.

lib/features/ai_digest/application/ai_digest_response_parser.dart

@@ -0,0 +1,175 @@
+import 'dart:convert';
+
+import 'package:relationship_saver/features/ai_digest/domain/ai_digest_models.dart';
+import 'package:uuid/uuid.dart';
+
+const Uuid _uuid = Uuid();
+
+class AiDigestParseResult {
+  const AiDigestParseResult({required this.drafts, this.error});
+
+  final List<AiSuggestionDraft> drafts;
+  final String? error;
+
+  bool get success => error == null;
+}
+
+class AiDigestResponseParser {
+  const AiDigestResponseParser({
+    this.maxItems = 10,
+    this.maxTitleChars = 90,
+    this.maxDetailsChars = 420,
+  });
+
+  final int maxItems;
+  final int maxTitleChars;
+  final int maxDetailsChars;
+
+  AiDigestParseResult parse({
+    required String response,
+    required Map<String, String> tokenToPersonId,
+    required String sourceRunId,
+    required DateTime suggestedAt,
+  }) {
+    try {
+      final Object? decoded = jsonDecode(_extractJson(response));
+      final List<dynamic> items = _extractItems(decoded);
+      final List<AiSuggestionDraft> drafts = <AiSuggestionDraft>[];
+
+      for (final dynamic item in items.take(maxItems)) {
+        if (item is! Map<String, dynamic>) {
+          continue;
+        }
+        final String? token = _string(item['personToken']);
+        final String? personId = token == null ? null : tokenToPersonId[token];
+        if (personId == null) {
+          continue;
+        }
+
+        final AiSuggestionKind? kind = _kind(item['kind']);
+        final String title = _trimAndCap(
+          _string(item['title']) ?? '',
+          maxTitleChars,
+        );
+        if (kind == null || title.isEmpty) {
+          continue;
+        }
+
+        drafts.add(
+          AiSuggestionDraft(
+            id: 'ai-${_uuid.v4()}',
+            personId: personId,
+            kind: kind,
+            title: title,
+            details: _trimAndCap(
+              _string(item['details']) ?? '',
+              maxDetailsChars,
+            ),
+            suggestedAt: suggestedAt,
+            suggestedFor:
+                _dateOrNull(item['suggestedFor']) ??
+                _dateOrNull(item['suggestedTiming']),
+            confidence: _confidence(item['confidence']),
+            status: AiSuggestionStatus.pending,
+            sourceRunId: sourceRunId,
+            reason: _trimAndCap(_string(item['reason']) ?? '', 240),
+          ),
+        );
+      }
+
+      if (drafts.isEmpty) {
+        return const AiDigestParseResult(
+          drafts: <AiSuggestionDraft>[],
+          error: 'No valid digest suggestions returned.',
+        );
+      }
+
+      return AiDigestParseResult(drafts: drafts);
+    } catch (error) {
+      return AiDigestParseResult(
+        drafts: const <AiSuggestionDraft>[],
+        error: 'Unable to parse digest response: $error',
+      );
+    }
+  }
+
+  String _extractJson(String response) {
+    final String trimmed = response.trim();
+    if (trimmed.startsWith('{') || trimmed.startsWith('[')) {
+      return trimmed;
+    }
+    final int objectStart = trimmed.indexOf('{');
+    final int arrayStart = trimmed.indexOf('[');
+    final int start = objectStart == -1
+        ? arrayStart
+        : arrayStart == -1
+        ? objectStart
+        : objectStart < arrayStart
+        ? objectStart
+        : arrayStart;
+    final int objectEnd = trimmed.lastIndexOf('}');
+    final int arrayEnd = trimmed.lastIndexOf(']');
+    final int end = objectEnd > arrayEnd ? objectEnd : arrayEnd;
+    if (start < 0 || end < start) {
+      throw const FormatException('No JSON object or array found.');
+    }
+    return trimmed.substring(start, end + 1);
+  }
+
+  List<dynamic> _extractItems(Object? decoded) {
+    if (decoded is List<dynamic>) {
+      return decoded;
+    }
+    if (decoded is Map<String, dynamic>) {
+      final Object? suggestions = decoded['suggestions'] ?? decoded['items'];
+      if (suggestions is List<dynamic>) {
+        return suggestions;
+      }
+    }
+    throw const FormatException('Digest response must be a JSON array.');
+  }
+
+  AiSuggestionKind? _kind(Object? raw) {
+    final String? value = _string(raw);
+    if (value == null) {
+      return null;
+    }
+    for (final AiSuggestionKind kind in AiSuggestionKind.values) {
+      if (kind.name == value) {
+        return kind;
+      }
+    }
+    return null;
+  }
+
+  String? _string(Object? raw) {
+    if (raw == null) {
+      return null;
+    }
+    final String value = '$raw'.trim();
+    return value.isEmpty ? null : value;
+  }
+
+  DateTime? _dateOrNull(Object? raw) {
+    final String? value = _string(raw);
+    if (value == null) {
+      return null;
+    }
+    return DateTime.tryParse(value)?.toLocal();
+  }
+
+  double _confidence(Object? raw) {
+    if (raw is num) {
+      return raw.toDouble().clamp(0.0, 1.0).toDouble();
+    }
+    return 0.5;
+  }
+
+  String _trimAndCap(String value, int maxChars) {
+    final String trimmed = value.trim();
+    if (trimmed.length <= maxChars) {
+      return trimmed;
+    }
+    return trimmed.substring(0, maxChars).trim();
+  }
+}