#201 Apps: Implement app registry service layer

## Parent Epic: #195 ## Description Create the service layer for app registry operations. ## Location engine/apps/registry.py ## AppRegistryService Class ### App CRUD - create_app(conn, publisher_id, app_data) -> App - get_app(conn, app_id) -> App | None - get_app_by_name(conn, publisher_id, app_name) -> App | None - list_apps(conn, filters, pagination) -> list[App] - update_app(conn, app_id, updates) -> App - delete_app(conn, app_id) -> bool (soft delete) ### Version Management - create_version(conn, app_id, version_data) -> AppVersion - get_version(conn, version_id) -> AppVersion | None - get_latest_version(conn, app_id, channel='stable') -> AppVersion - list_versions(conn, app_id) -> list[AppVersion] - publish_version(conn, version_id) -> AppVersion - deprecate_version(conn, version_id) -> AppVersion ### Installation Management - install_app(conn, tenant_id, app_id, version_id, config) -> Installation - uninstall_app(conn, tenant_id, app_id) -> bool - get_installation(conn, tenant_id, app_id) -> Installation - list_installations(conn, tenant_id) -> list[Installation] - update_installation_config(conn, installation_id, config) -> Installation - upgrade_installation(conn, installation_id, version_id) -> Installation - enable_app(conn, installation_id) -> Installation - disable_app(conn, installation_id) -> Installation ### App Discovery - search_apps(conn, query, category, tags) -> list[App] - list_categories(conn) -> list[str] - get_marketplace_apps(conn, visibility='public') -> list[App] ### Secrets Management - set_app_secret(conn, tenant_id, app_id, secret_name, secret_path) -> bool - delete_app_secret(conn, tenant_id, app_id, secret_name) -> bool - list_app_secrets(conn, tenant_id, app_id) -> list[str] ### Execution Logging - log_execution(conn, log_data) -> None - get_execution_logs(conn, filters, pagination) -> list[ExecutionLog] ## Data Classes - App, AppVersion, Installation, ExecutionLog - Use dataclasses for type safety ## SQL Queries All queries in engine/sql/queries/apps.sql per guideline ## Testing - Full CRUD tests - Pagination tests - Filter tests - Concurrent access tests