feat: make polling interval configurable via lettabot.yaml (#181)

Add `pollIntervalSec` to the Google integration config so the email
polling interval can be set in lettabot.yaml instead of requiring
the POLLING_INTERVAL_MS environment variable.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/config/io.ts

@@ -173,6 +173,9 @@ export function configToEnv(config: LettaBotConfig): Record<string, string> {
   if (config.integrations?.google?.enabled && config.integrations.google.account) {
     env.GMAIL_ACCOUNT = config.integrations.google.account;
   }
+  if (config.integrations?.google?.pollIntervalSec) {
+    env.POLLING_INTERVAL_MS = String(config.integrations.google.pollIntervalSec * 1000);
+  }
 
   if (config.attachments?.maxMB !== undefined) {
     env.ATTACHMENTS_MAX_MB = String(config.attachments.maxMB);

src/config/types.ts

@@ -121,6 +121,7 @@ export interface GoogleConfig {
   enabled: boolean;
   account?: string;
   services?: string[];  // e.g., ['gmail', 'calendar', 'drive', 'contacts', 'docs', 'sheets']
+  pollIntervalSec?: number;  // Polling interval in seconds (default: 60)
 }
 
 // Default config