[FE] Create 'View only' post - No validation check for website links

[SharaWong]

- In TW, there is no validation check of empty inputs for the website links

In PG, if either of the textbox is filled, it will immediately show the error message for the other.

- There is no validation check when I straight enter the URL

In PG, once you start enter the URL, the validation will happen

[guangshinhaha]

PR #55 adds client-side validation for the website link fields:

• Cross-field: if either URL or description is filled, the other becomes required (inline error shown immediately)
• URL format: validates that the URL is a valid http:// or https:// URL

⚠️ PGW cross-check still needed — these rules were inferred from the PG screenshots in this issue since we're running in mock mode. Before merging, we need to verify against PGW's actual FE/BE:

1. Does PGW require both fields when either is filled, or does it allow URL-only submission?
2. Does PGW validate URL format client-side or only server-side?
3. Does PGW restrict to http(s):// or allow other protocols (e.g. tel:, mailto:)?