feat: session start screen, question context input, and G4F-style AI multi-provider fallback

lib/models/history_entry_model.dart

@@ -7,6 +7,8 @@ class HistoryEntry {
   final String symbolicMeaning;
   final String readingType;
   final String? positionTitle;
+  final String? question;
+  final String? aiInterpretation;
 
   const HistoryEntry({
     required this.id,
@@ -17,8 +19,36 @@ class HistoryEntry {
     required this.symbolicMeaning,
     this.readingType = 'Жребий',
     this.positionTitle,
+    this.question,
+    this.aiInterpretation,
   });
 
+  HistoryEntry copyWith({
+    String? id,
+    DateTime? timestamp,
+    String? word,
+    int? sessionNumber,
+    String? partOfSpeech,
+    String? symbolicMeaning,
+    String? readingType,
+    String? positionTitle,
+    String? question,
+    String? aiInterpretation,
+  }) {
+    return HistoryEntry(
+      id: id ?? this.id,
+      timestamp: timestamp ?? this.timestamp,
+      word: word ?? this.word,
+      sessionNumber: sessionNumber ?? this.sessionNumber,
+      partOfSpeech: partOfSpeech ?? this.partOfSpeech,
+      symbolicMeaning: symbolicMeaning ?? this.symbolicMeaning,
+      readingType: readingType ?? this.readingType,
+      positionTitle: positionTitle ?? this.positionTitle,
+      question: question ?? this.question,
+      aiInterpretation: aiInterpretation ?? this.aiInterpretation,
+    );
+  }
+
   String get formattedSessionNumber => sessionNumber.toString().padLeft(3, '0');
 
   String get formattedDate {
@@ -41,6 +71,8 @@ class HistoryEntry {
       'symbolicMeaning': symbolicMeaning,
       'readingType': readingType,
       'positionTitle': positionTitle,
+      'question': question,
+      'aiInterpretation': aiInterpretation,
     };
   }
 
@@ -54,6 +86,8 @@ class HistoryEntry {
       symbolicMeaning: map['symbolicMeaning'] as String? ?? '',
       readingType: map['readingType'] as String? ?? 'Жребий',
       positionTitle: map['positionTitle'] as String?,
+      question: map['question'] as String?,
+      aiInterpretation: map['aiInterpretation'] as String?,
     );
   }
 }