feat(prompt-optimizer): add prompt optimization APIs and database tables

- Added API endpoints for prompt optimization:
  * POST /prompt/sessions: Create a new prompt optimization session
  * GET /prompt/sessions/{session_id}: Retrieve session message history
  * POST /prompt/sessions/{session_id}/messages: Send message and get optimized prompt
  * PUT /prompt/model: Create or update system prompt model configuration

- Added database models for prompt optimization:
  * prompt_opt_session: Stores session metadata
  * prompt_opt_session_history: Stores session message history
  * prompt_opt_message: Stores user and assistant messages
  * prompt_opt_model_config: Stores system prompt model configurations

- Updated service layer to handle message creation, prompt optimization, and variable parsing
- Added corresponding Pydantic schemas for request and response validation

api/app/models/__init__.py

@@ -20,6 +20,7 @@ from .data_config_model import DataConfig
 from .multi_agent_model import MultiAgentConfig, AgentInvocation
 from .workflow_model import WorkflowConfig, WorkflowExecution, WorkflowNodeExecution
 from .retrieval_info import RetrievalInfo
+from .prompt_optimizer_model import PromptOptimizerModelConfig, PromptOptimizerSession, PromptOptimizerSessionHistory
 
 __all__ = [
     "Tenants",
@@ -54,5 +55,8 @@ __all__ = [
     "WorkflowConfig",
     "WorkflowExecution",
     "WorkflowNodeExecution",
-    "RetrievalInfo"
+    "RetrievalInfo",
+    "PromptOptimizerModelConfig",
+    "PromptOptimizerSession",
+    "PromptOptimizerSessionHistory"
 ]