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.

frontend/src/hooks/use-voice-preview.ts

@@ -50,6 +50,7 @@ type VideoNetworkMetrics = {
 type ConnectOptions = {
   visionEnabled?: boolean;
   videoStream?: MediaStream | null;
+  dynamicVariables?: Record<string, string | number | boolean>;
 };
 
 export type ChatMessage = {
@@ -519,6 +520,7 @@ export function useVoicePreview(
                 type: localDescription.type,
                 assistant_id: assistantId,
                 vision_enabled: Boolean(options.visionEnabled),
+                dynamic_variables: options.dynamicVariables ?? {},
               },
             }),
           );