feat(saas): Phase 4 端到端完善 — 设备注册、离线支持、配置迁移、集成测试

- 后端: devices 表 + register/heartbeat/list 端点 (UPSERT 语义)
- 桌面端: 设备 ID 持久化 + 5 分钟心跳 + 离线状态指示
- saas-client: 重试逻辑 (2 次指数退避) + isServerReachable 跟踪
- ConfigMigrationWizard: 3 步向导 (方向选择→冲突解决→结果)
- SaaSSettings: 修改密码折叠面板 + 迁移向导入口
- 集成测试: 21 个测试全部通过 (含设备注册/UPSERT/心跳、密码修改、E2E 生命周期)
- 修复 ConfigMigrationWizard merge 分支变量遮蔽 bug

crates/zclaw-saas/src/db.rs

@@ -195,6 +195,21 @@ CREATE TABLE IF NOT EXISTS config_sync_log (
     created_at TEXT NOT NULL
 );
 CREATE INDEX IF NOT EXISTS idx_sync_account ON config_sync_log(account_id);
+
+CREATE TABLE IF NOT EXISTS devices (
+    id TEXT PRIMARY KEY,
+    account_id TEXT NOT NULL,
+    device_id TEXT NOT NULL,
+    device_name TEXT,
+    platform TEXT,
+    app_version TEXT,
+    last_seen_at TEXT NOT NULL,
+    created_at TEXT NOT NULL,
+    FOREIGN KEY (account_id) REFERENCES accounts(id) ON DELETE CASCADE
+);
+CREATE INDEX IF NOT EXISTS idx_devices_account ON devices(account_id);
+CREATE INDEX IF NOT EXISTS idx_devices_device_id ON devices(device_id);
+CREATE UNIQUE INDEX IF NOT EXISTS idx_devices_unique ON devices(account_id, device_id);
 "#;
 
 const SEED_ROLES: &str = r#"
@@ -319,7 +334,7 @@ mod tests {
         let tables = [
             "accounts", "api_tokens", "roles", "permission_templates",
             "operation_logs", "providers", "models", "account_api_keys",
-            "usage_records", "relay_tasks", "config_items", "config_sync_log",
+            "usage_records", "relay_tasks", "config_items", "config_sync_log", "devices",
         ];
         for table in tables {
             let count: (i64,) = sqlx::query_as(&format!(