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/src/logging-client.ts

@@ -0,0 +1,23 @@
+import type {
+  ClientSendParams,
+  ClientSendResult,
+  EmailClient,
+} from "./types.js";
+
+let messageIdCounter = 0;
+
+export function createLoggingEmailClient(): EmailClient {
+  return {
+    sendEmail: (params: ClientSendParams): Promise<ClientSendResult> => {
+      console.log("=== DEV MODE EMAIL ===");
+      console.log(`From: ${params.from}`);
+      console.log(`To: ${params.to}`);
+      console.log(`Subject: ${params.subject}`);
+      console.log(`Text Body:\n${params.textBody}`);
+      console.log("======================");
+
+      messageIdCounter++;
+      return Promise.resolve({ messageId: `dev-mode-${messageIdCounter.toString()}` });
+    },
+  };
+}