feat(messaging): implement Outbox persistence with three-tier sync strategy

Add Outbox pattern for reliable message sending with offline recovery:

- Persist pending/failed messages to SQLite (status field extended with 'pending'|'failed')
- App restart scans pending messages and auto-retries failed sends
- Add versioned migration system (PRAGMA user_version) for future schema evolution

Implement three-tier sync strategy for precision and efficiency:

- syncByVersion: precise incremental sync using persisted cursor (Matrix-style)
- syncBySeq: fallback seq-based incremental sync
- Full refresh: last resort for recovery

Add conversation sync state machine for UI error visibility:

- 'idle' | 'hydrating' | 'synced' | 'error' states exposed via useMessages hook
- Enables loading/error indicators during hydration pipeline

Standardize error handling across message services using createErrorHandler.

Add tests: messageOutbox.test.ts, syncByVersion.test.ts, syncState.test.ts

src/stores/message/__tests__/syncByVersion.test.ts

@@ -0,0 +1,117 @@
+/**
+ * syncByVersion 游标同步单测（批次二③）
+ *
+ * 锁定基于版本号的精确增量恢复不变量：
+ * 1. 成功同步并推进持久化游标
+ * 2. full_sync=true 时退化（返回 false）
+ * 3. 异常时退化（返回 false）
+ * 4. 无 version（<=0）时直接退化
+ *
+ * 对标 Matrix resume 游标：断线恢复从全量轮询升级为精确增量。
+ */
+
+import { useMessageStore } from '../store';
+import { MessageSyncService } from '../services/MessageSyncService';
+import { messageService } from '@/services/message';
+import { messageRepository } from '@/database';
+
+function createSyncService(): MessageSyncService {
+  return new MessageSyncService(
+    () => 'me',
+    { markAsRead: async () => {}, markAllAsRead: async () => {} } as any,
+    { getSenderInfo: async () => null, enrichMessagesWithSenderInfo: () => {} } as any,
+    undefined
+  );
+}
+
+describe('syncByVersion 游标同步', () => {
+  beforeEach(() => {
+    useMessageStore.getState().reset();
+    (messageRepository as any).__reset();
+    (messageService as any).__reset();
+  });
+
+  it('无变更时返回成功且推进游标', async () => {
+    const serviceMock = messageService as any;
+    serviceMock.__setSyncByVersionHandler((version: number) => ({
+      current_version: version + 10,
+      changes: [],
+      full_sync: false,
+      has_more: false,
+    }));
+
+    const sync = createSyncService();
+    const ok = await sync.syncByVersion(100);
+
+    expect(ok).toBe(true);
+    // 游标推进到 current_version
+    expect(useMessageStore.getState().syncVersion).toBe(110);
+  });
+
+  it('full_sync=true 时退化为 false', async () => {
+    const serviceMock = messageService as any;
+    serviceMock.__setSyncByVersionHandler(() => ({
+      current_version: 0,
+      changes: [],
+      full_sync: true,
+      has_more: false,
+    }));
+
+    const sync = createSyncService();
+    const ok = await sync.syncByVersion(100);
+
+    expect(ok).toBe(false);
+  });
+
+  it('API 抛异常时退化为 false', async () => {
+    const serviceMock = messageService as any;
+    serviceMock.__setSyncByVersionHandler(() => {
+      throw new Error('网络故障');
+    });
+
+    const sync = createSyncService();
+    const ok = await sync.syncByVersion(100);
+
+    expect(ok).toBe(false);
+  });
+
+  it('version <= 0 时直接退化', async () => {
+    const sync = createSyncService();
+    const ok1 = await sync.syncByVersion(0);
+    const ok2 = await sync.syncByVersion(-1);
+    expect(ok1).toBe(false);
+    expect(ok2).toBe(false);
+  });
+
+  it('有会话变更时按需同步会话详情', async () => {
+    const serviceMock = messageService as any;
+    // 先在 store 放一个会话，让 fetchConversationDetail 有上下文
+    useMessageStore.getState().setConversationsWithUnread(
+      new Map([['c1', { id: 'c1', last_seq: 5, unread_count: 0 } as any]]),
+      0, 0
+    );
+
+    let detailCalled = false;
+    serviceMock.__setSyncByVersionHandler((version: number) => ({
+      current_version: version + 5,
+      changes: [
+        { conversation_id: 'c1', change_type: 'new_message', max_seq: 10, version: version + 1 },
+      ],
+      full_sync: false,
+      has_more: false,
+    }));
+    // fetchConversationDetail 内部调 getConversationById
+    serviceMock.getConversationById = async () => {
+      detailCalled = true;
+      return { id: 'c1', last_seq: 10 } as any;
+    };
+    serviceMock.getMessages = async () => ({ messages: [], total: 0, page: 1, page_size: 20 });
+
+    const sync = createSyncService();
+    const ok = await sync.syncByVersion(100);
+
+    expect(ok).toBe(true);
+    expect(detailCalled).toBe(true);
+    expect(useMessageStore.getState().syncVersion).toBe(105);
+  });
+});