feat: add dynamic variables and startup result handling in batch run schemas

- Introduced dynamic_variables field in BatchRunCreate schema to support flexible input types.
- Added BatchStartupResult schema to encapsulate startup state, including greeting and auto-confirmed messages.
- Updated BatchRunCaseOut schema to include startup results, enhancing the structure for test run outputs.
- Enhanced test run orchestration to prepare and validate dynamic configurations, ensuring isolated variable management across test cases.
- Implemented changes in the frontend to accommodate new data structures for improved test case execution and result tracking.

frontend/src/lib/api.ts

@@ -851,6 +851,7 @@ export const batchRunsApi = {
     assistantId: string;
     evaluatorModelResourceId: string;
     caseIds: string[];
+    dynamicVariables?: Record<string, string | number | boolean>;
     title?: string;
     config: {
       concurrency: number;