Profile settings: Strengthen profile settings validation messaging and add social link pre-validation

[nitinawari]

Issue Description

Profile settings currently return generic HTTP 400 failures for some invalid payloads, which hides actionable validation details from users.

The goal is to improve validation UX by surfacing clear, field-relevant messages before/at submit time instead of relying on backend 400 responses alone.

Context

This is a validation quality improvement, not a bug about duplicate error containers in the existing codebase.

Main focus areas:

• Show meaningful validation feedback instead of generic 400-style failure experience.
• Add stronger social link validation in UI before submitting.

Scope

• Improve save flow so validation failures show clear error messages.
• For social links, validate client-side and prevent invalid submits.
• Preserve existing successful-save behavior and current field flows.