fix: correct simulation API field names

The backend expects 'check_interval' not 'interval_seconds',
and 'chain' is required.

src/frontend/src/lib/api/client.ts

@@ -189,7 +189,7 @@ export const api = {
 	},
 
 	simulate: {
-		async start(botId: string, config: { token: string; interval_seconds: number; auto_execute: boolean }): Promise<Simulation> {
+		async start(botId: string, config: { token: string; chain?: string; check_interval: number; auto_execute: boolean }): Promise<Simulation> {
 			const response = await fetch(`${API_URL}/bots/${botId}/simulate`, {
 				method: 'POST',
 				headers: getAuthHeaders(),

src/frontend/src/routes/bot/[id]/simulate/+page.svelte

@@ -68,7 +68,8 @@
 		try {
 			const simulation = await api.simulate.start(botId, {
 				token: tokenAddress,
-				interval_seconds: intervalSeconds,
+				chain: 'bsc',
+				check_interval: intervalSeconds,
 				auto_execute: autoExecute
 			});
 			setCurrentSimulation(simulation);