Extract emails into separate package with clean interface

- Create packages/emails/ with EmailClient interface abstraction
- Wrap Postmark ServerClient in adapter for clean typing
- Add createLoggingEmailClient for dev mode (logs to console)
- Split email templates into individual files with full test coverage
- Update api-server to use new package via context injection
- Remove EMAIL_DEV_MODE - now uses POSTMARK_API_KEY presence
- Delete apps/api-server/src/utils/email.ts

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

packages/emails/eslint.config.js

@@ -0,0 +1,12 @@
+import { configs } from "@macalinao/eslint-config";
+
+export default [
+  ...configs.fast,
+  {
+    languageOptions: {
+      parserOptions: {
+        tsconfigRootDir: import.meta.dirname,
+      },
+    },
+  },
+];