fix: signup form broken in production (#10206)

`vue-i18n` has a new [linked message
format](https://vue-i18n.intlify.dev/guide/essentials/syntax#linked-messages),
this however conflicts with raw usage an email address like
`hey@chatwoot.com`. The way to solve this as prescribed by then is to
use [literal
interpolation](https://vue-i18n.intlify.dev/guide/essentials/syntax#literal-interpolation),
like `hey{'@'}chatwoot.com`.

This PR does that for the entire translation files

app/javascript/dashboard/i18n/locale/sr/login.json

@@ -3,7 +3,7 @@
     "TITLE": "Login to Chatwoot",
     "EMAIL": {
       "LABEL": "E-pošta",
-      "PLACEHOLDER": "example@companyname.com",
+      "PLACEHOLDER": "example{'@'}companyname.com",
       "ERROR": "Molim vas unesite ispravnu adresu e-pošte"
     },
     "PASSWORD": {

app/javascript/dashboard/i18n/locale/sr/signup.json

@@ -20,7 +20,7 @@
     },
     "EMAIL": {
       "LABEL": "Poslovna e-pošta",
-      "PLACEHOLDER": "Enter your work email address. E.g., bruce@wayne.enterprises",
+      "PLACEHOLDER": "Enter your work email address. E.g., bruce{'@'}wayne{'.'}enterprises",
       "ERROR": "Please enter a valid work email address."
     },
     "PASSWORD": {