Fix Kan build failure (TS7016 nodemailer)

[michelroegl-brunner]

✍️ Description

Kan install/update fails at pnpm build --filter=@kan/web because @kan/email cannot compile: TypeScript reports TS7016 for nodemailer (missing declaration file).

The upstream Kan repo already includes @types/nodemailer in devDependencies. Our scripts source /opt/kan/.env (which sets NODE_ENV=production) before pnpm install, so pnpm skips devDependencies.

This PR adds --prod=false to pnpm install in install/kan-install.sh and ct/kan.sh so dev deps (including @types/nodemailer, typescript, and workspace tooling) are installed for the build. Runtime still uses NODE_ENV=production via systemd EnvironmentFile.

🔗 Related Issue

Fixes #

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to script metadata (PocketBase/website data).
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.