Update email configuration in README and enhance email handler for Microsoft 365 support

- Updated the README.md to include specific SMTP settings for Microsoft 365 and OAuth2 authentication options.
- Modified the email handler to support OAuth2 authentication for Microsoft 365, improving security and flexibility.
- Enhanced logging to provide clearer feedback on email configuration and authentication methods used.

src/env.d.ts

@@ -16,6 +16,10 @@ interface ImportMetaEnv {
   readonly WEBSITE_NAME?: string;
   readonly GEMINI_API_KEY?: string;
   readonly MANUAL_REVIEW_SECRET?: string;
+  readonly OAUTH2_CLIENT_ID?: string;
+  readonly OAUTH2_CLIENT_SECRET?: string;
+  readonly OAUTH2_REFRESH_TOKEN?: string;
+  readonly OAUTH2_ACCESS_TOKEN?: string;
 }
 
 interface ImportMeta {