Add dynamic variable support to Assistant model and related components

- Introduce dynamic variable definitions in AssistantConfig and Assistant models, allowing for flexible prompt customization.
- Implement validation for dynamic variable names and types in the schema.
- Update backend services and routes to handle dynamic variables in assistant configurations and runtime processing.
- Enhance frontend components to support dynamic variable definitions, including a new editor for managing variables.
- Add tests to ensure proper functionality and validation of dynamic variables in various scenarios.

backend/routes/assistants.py

@@ -154,6 +154,7 @@ async def _to_out(session: AsyncSession, assistant: Assistant) -> AssistantOut:
         knowledge_retrieval_config=assistant.knowledge_retrieval_config or {},
         tool_ids=await _tool_ids(session, assistant.id),
         prompt=assistant.prompt,
+        dynamic_variable_definitions=assistant.dynamic_variable_definitions or {},
         api_url=assistant.api_url,
         api_key=mask(assistant.api_key),
         app_id=assistant.app_id,
@@ -220,6 +221,7 @@ async def duplicate_assistant(
         knowledge_base_id=source.knowledge_base_id,
         knowledge_retrieval_config=dict(source.knowledge_retrieval_config or {}),
         prompt=source.prompt,
+        dynamic_variable_definitions=dict(source.dynamic_variable_definitions or {}),
         api_url=source.api_url,
         api_key=source.api_key,
         app_id=source.app_id,