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/tsconfig.json

@@ -0,0 +1,6 @@
+{
+  "extends": "@macalinao/tsconfig/tsconfig.base.json",
+  "compilerOptions": {
+    "types": ["bun"]
+  }
+}