feat: 添加首页图片选择功能（拍照/相册）

apps/lib/features/chat/data/services/ag_ui_service.dart

@@ -3,6 +3,7 @@ import 'dart:convert';
 import 'dart:math';
 
 import 'package:dio/dio.dart';
+import 'package:image_picker/image_picker.dart';
 import 'package:social_app/core/api/i_api_client.dart';
 import 'package:social_app/core/api/mock_api_client.dart';
 
@@ -41,9 +42,9 @@ class AgUiService {
     }
   }
 
-  Future<void> sendMessage(String content) async {
+  Future<void> sendMessage(String content, {List<XFile>? images}) async {
     final streamToken = ++_activeStreamToken;
-    final runInput = _buildRunInput(content: content);
+    final runInput = await _buildRunInput(content: content, images: images);
     final response = await _apiClient.post<Map<String, dynamic>>(
       '/api/v1/agent/runs',
       data: runInput,
@@ -238,15 +239,50 @@ class AgUiService {
     }
   }
 
-  Map<String, dynamic> _buildRunInput({required String content}) {
+  Future<Map<String, dynamic>> _buildRunInput({
+    required String content,
+    List<XFile>? images,
+  }) async {
     final threadId = _threadId ?? _newUuid();
     final runId = _nextId(_runIdPrefix);
+
+    final contentBlocks = <Map<String, dynamic>>[];
+
+    if (content.isNotEmpty) {
+      contentBlocks.add({'type': 'text', 'text': content});
+    }
+
+    if (images != null && images.isNotEmpty) {
+      for (final image in images) {
+        final bytes = await image.readAsBytes();
+        final base64 = base64Encode(bytes);
+        contentBlocks.add({
+          'type': 'image',
+          'source': {
+            'type': 'base64',
+            'media_type': 'image/jpeg',
+            'data': base64,
+          },
+        });
+      }
+    }
+
+    final dynamic messageContent;
+    if (contentBlocks.isEmpty) {
+      messageContent = '';
+    } else if (contentBlocks.length == 1 &&
+        contentBlocks[0]['type'] == 'text') {
+      messageContent = contentBlocks[0]['text'];
+    } else {
+      messageContent = contentBlocks;
+    }
+
     return {
       'threadId': threadId,
       'runId': runId,
       'state': <String, dynamic>{},
       'messages': [
-        {'id': _nextId('user_'), 'role': 'user', 'content': content},
+        {'id': _nextId('user_'), 'role': 'user', 'content': messageContent},
       ],
       'tools': _buildTools(),
       'context': <Map<String, dynamic>>[],