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-lock.json

@@ -17,7 +17,8 @@
         "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",
@@ -3743,6 +3744,12 @@
         "node": ">=10"
       }
     },
+    "node_modules/server-only": {
+      "version": "0.0.1",
+      "resolved": "https://registry.npmjs.org/server-only/-/server-only-0.0.1.tgz",
+      "integrity": "sha512-qepMx2JxAa5jjfzxG79yPPq+8BuFToHd1hm7kI+Z4zAq1ftQiP7HcxMhDDItrbtwVeLg/cY2JnKnrcFkmiswNA==",
+      "license": "MIT"
+    },
     "node_modules/sharp": {
       "version": "0.34.5",
       "resolved": "https://registry.npmjs.org/sharp/-/sharp-0.34.5.tgz",