refactor(env): unify required-env validation through useRuntimeConfig

validate-env.js now reads all four required vars (MONGODB_URI, JWT_SECRET,
RESEND_API_KEY, HELCIM_API_TOKEN) from useRuntimeConfig() instead of mixing
direct process.env reads with a JWT-only special case. Mongoose and the six
Resend instantiations follow suit. Either bare or NUXT_-prefixed env names
are accepted, so Dokploy no longer needs duplicate entries.

server/utils/magicLink.js

@@ -6,7 +6,7 @@ import { randomUUID } from 'crypto'
 import { Resend } from 'resend'
 import Member from '../models/member.js'
 
-const resend = new Resend(process.env.RESEND_API_KEY)
+const resend = new Resend(useRuntimeConfig().resendApiKey)
 
 /**
  * Issue a 15-minute magic-link JWT for `email` and email it.