fix(pitch-deck): split email.ts to fix client bundle including nodemailer

Client component (investors/new page) imported DEFAULT_MESSAGE etc. from
lib/email.ts which also top-level initialises nodemailer — webpack tried
to bundle fs/net/dns into the client chunk and failed.

Extract the pure constants + getDefaultGreeting into lib/email-templates.ts
(client-safe), keep nodemailer in lib/email.ts (server-only), update the
page to import from email-templates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pitch-deck/package.json

@@ -20,7 +20,8 @@
     "pg": "^8.13.1",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
-    "recharts": "^2.15.0"
+    "recharts": "^2.15.0",
+    "server-only": "^0.0.1"
   },
   "devDependencies": {
     "@types/bcryptjs": "^2.4.6",