feat(webDev): add inquiry modal for pricing plans

This commit introduces a 'Contact Sales' modal on the web development page, allowing users to inquire about specific service plans.

- The pricing plan buttons now trigger this modal, pre-filled with the selected plan's details.
- Users can add custom remarks to their inquiry.
- On submission, a pre-formatted message is generated and opened in WhatsApp using a new `useWhatsAppMsgSender` composable.
- Adds `NUXT_PUBLIC_WHATSAPP_NUMBER` to the runtime configuration.
- Refactors content validation by introducing Zod schemas for `PricingPlan` and `Button` props to improve type safety.
- Adds new i18n keys for the modal interface and message templates.

app/layouts/default.vue

@@ -3,7 +3,7 @@
     <UHeader
       :ui="{
         left: 'flex items-center gap-1.5',
-        center: 'hidden lg:flex lg:flex-16',
+        center: 'hidden lg:flex lg:flex-4',
         right: 'flex items-center justify-end gap-1.5',
       }"
     >