feat: add OpenAI types and AI caller utility

- Consolidate OpenAI types to types.ts
- Create reusable callOpenAI() function
- Add tool call parsing and result handling

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/utils/index.ts

@@ -0,0 +1,15 @@
+export * from './logger';
+export * from './session-manager';
+export * from './ai-caller';
+export * from './formatters';
+export * from './patterns';
+export * from './retry';
+export * from './circuit-breaker';
+export * from './metrics';
+export * from './optimistic-lock';
+export * from './api-helper';
+export * from './api-urls';
+export * from './env-validation';
+export * from './error';
+export * from './email-decoder';
+export * from './reconciliation';