fix(ui): add regex validation for DLE form, resolve infinite loading for instances (#535)

Description

Must be a match of regex '[a-z](?:[-a-z0-9]{0,61}[a-z0-9])?|[1-9][0-9]{0,19}'

Related issue

#535 (closed)

https://postgres-ai.slack.com/archives/CSXS2JV6W/p1691436837314509

Examples

Checklist

• MR description has been reviewed
• MR changes are functionally tested
• MR does NOT have API/CLI changes OR there are API/CLI changes and they have been reviewed & DOCS ARE ADJUSTED (reference doc, etc)
• MR does NOT have UI changes OR there are UI changes and they have been reviewed & UX IS REVIEWED

Closes #535 (closed)