feat(core): add OpenClaw to AppType enum and database schema

- Add OpenClaw variant to AppType enum
- Update is_additive_mode() to return true for OpenClaw
- Update McpApps, SkillApps, McpRoot, PromptRoot structs
- Add database migration v5 to v6 for enabled_openclaw columns
- Update mcp_servers and skills table definitions

src-tauri/src/database/mod.rs

@@ -48,7 +48,7 @@ const DB_BACKUP_RETAIN: usize = 10;
 
 /// 当前 Schema 版本号
 /// 每次修改表结构时递增，并在 schema.rs 中添加相应的迁移逻辑
-pub(crate) const SCHEMA_VERSION: i32 = 5;
+pub(crate) const SCHEMA_VERSION: i32 = 6;
 
 /// 安全地序列化 JSON，避免 unwrap panic
 pub(crate) fn to_json_string<T: Serialize>(value: &T) -> Result<String, AppError> {