feat(settings): 编辑个人资料头像上传全量实现（#49 / #50）

- EditProfileState: 新增 isUploadingAvatar 字段
- EditProfileViewModel: pickAndUploadAvatar()（ImagePicker→裁剪→CDN→state）
- EditProfilePage: 完整重写
  - 88pt 圆形头像 + 8色渐变占位 + 相机角标 + 上传进度环
  - _showAvatarSourceSheet()（相册 / 拍照）
  - Card 分组表单：昵称（50字计数）/ 个人简介（200字多行）
  - 保存按钮（昵称空或上传中禁用）
  - 错误 Banner
  - 保存成功 → 刷新 SettingsViewModel + pop

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

apps/im_app/lib/features/settings/presentation/edit_profile_view_model.dart

@@ -1,14 +1,22 @@
-import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'dart:io';
 
+import 'package:flutter/foundation.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:image_cropper/image_cropper.dart';
+import 'package:image_picker/image_picker.dart';
+
+import 'package:im_app/app/di/network_provider.dart';
+import 'package:im_app/data/remote/upload_file_request.dart';
 import 'package:im_app/features/settings/di/settings_providers.dart';
 
-/// 编辑个人资料页状态
+/// 编辑个人资料页状态（#49 / #50）
 class EditProfileState {
   final String nickname;
   final String bio;
   final String? avatarUrl;
   final bool isLoading;
   final bool isSaving;
+  final bool isUploadingAvatar;
   final String? error;
 
   const EditProfileState({
@@ -17,6 +25,7 @@ class EditProfileState {
     this.avatarUrl,
     this.isLoading = false,
     this.isSaving = false,
+    this.isUploadingAvatar = false,
     this.error,
   });
 
@@ -27,6 +36,7 @@ class EditProfileState {
     bool clearAvatarUrl = false,
     bool? isLoading,
     bool? isSaving,
+    bool? isUploadingAvatar,
     String? error,
     bool clearError = false,
   }) {
@@ -36,12 +46,36 @@ class EditProfileState {
       avatarUrl: clearAvatarUrl ? null : (avatarUrl ?? this.avatarUrl),
       isLoading: isLoading ?? this.isLoading,
       isSaving: isSaving ?? this.isSaving,
+      isUploadingAvatar: isUploadingAvatar ?? this.isUploadingAvatar,
       error: clearError ? null : (error ?? this.error),
     );
   }
 }
 
-/// 编辑个人资料 ViewModel
+/// 编辑个人资料 ViewModel（#49 / #50）
+///
+/// ## 数据流
+/// ```
+/// EditProfilePage (build)
+///   └─ ref.watch(editProfileViewModelProvider) 读取 nickname/bio/avatarUrl
+///
+/// 初始化：
+///   _loadCurrentProfile()
+///     → FetchProfileUseCase.execute() → GET /app/api/user/profile
+///     → 填充 nickname, bio, avatarUrl
+///
+/// 头像上传（#49）：
+///   pickAndUploadAvatar()
+///     → ImagePicker.pickImage(gallery | camera)
+///     → ImageCropper.cropImage() （iOS UIImagePickerController 圆形预览）
+///     → UploadFileRequest FormData → POST /app/api/upload/file
+///     → state.avatarUrl = result.url
+///
+/// 保存：
+///   save()
+///     → UpdateProfileUseCase.execute(nickname, bio, profilePicUrl)
+///     → POST /app/api/user/update-profile
+/// ```
 class EditProfileViewModel extends Notifier<EditProfileState> {
   @override
   EditProfileState build() {
@@ -49,6 +83,8 @@ class EditProfileViewModel extends Notifier<EditProfileState> {
     return const EditProfileState(isLoading: true);
   }
 
+  // ── 初始化 ────────────────────────────────────────────────────────────────
+
   Future<void> _loadCurrentProfile() async {
     try {
       final profile = await ref.read(fetchProfileUseCaseProvider).execute();
@@ -63,6 +99,8 @@ class EditProfileViewModel extends Notifier<EditProfileState> {
     }
   }
 
+  // ── 字段更新 ──────────────────────────────────────────────────────────────
+
   void updateNickname(String value) {
     state = state.copyWith(nickname: value, clearError: true);
   }
@@ -71,8 +109,64 @@ class EditProfileViewModel extends Notifier<EditProfileState> {
     state = state.copyWith(bio: value);
   }
 
-  // TODO Issue #6: 头像上传（CDN 流程）
-  // void pickAndUploadAvatar() async { ... }
+  // ── 头像选取与上传（#49） ──────────────────────────────────────────────────
+
+  /// 弹出选图 Sheet（相册 / 拍照）→ 裁剪 → 上传 CDN → 更新预览
+  ///
+  /// 上传中 [isUploadingAvatar] = true，完成后恢复 false。
+  /// 失败时设置 [error]（由 UI 显示 SnackBar）。
+  Future<void> pickAndUploadAvatar(ImageSource source) async {
+    final picker = ImagePicker();
+    final picked = await picker.pickImage(
+      source: source,
+      maxWidth: 900,
+      maxHeight: 900,
+      imageQuality: 85,
+    );
+    if (picked == null) return;
+
+    // 圆形裁剪（iOS UIImagePickerController 圆形预览对齐）
+    final cropped = await ImageCropper().cropImage(
+      sourcePath: picked.path,
+      aspectRatio: const CropAspectRatio(ratioX: 1, ratioY: 1),
+      uiSettings: [
+        IOSUiSettings(
+          title: '裁剪头像',
+          aspectRatioLockEnabled: true,
+          resetAspectRatioEnabled: false,
+          rotateButtonsHidden: false,
+        ),
+        AndroidUiSettings(
+          toolbarTitle: '裁剪头像',
+          lockAspectRatio: true,
+        ),
+      ],
+    );
+    if (cropped == null) return;
+
+    state = state.copyWith(isUploadingAvatar: true, clearError: true);
+    try {
+      final result = await ref.read(networkSdkApiProvider).executeRequest(
+        UploadFileRequest(filePath: cropped.path),
+      );
+      final url = result?.url ?? '';
+      if (url.isEmpty) throw Exception('上传返回空 URL');
+      state = state.copyWith(isUploadingAvatar: false, avatarUrl: url);
+    } catch (e) {
+      debugPrint('[EditProfileViewModel] avatar upload error: $e');
+      state = state.copyWith(
+        isUploadingAvatar: false,
+        error: '头像上传失败: $e',
+      );
+    } finally {
+      // 清理临时裁剪文件
+      try {
+        await File(cropped.path).delete();
+      } catch (_) {}
+    }
+  }
+
+  // ── 保存 ──────────────────────────────────────────────────────────────────
 
   Future<bool> save() async {
     if (state.nickname.trim().isEmpty) {