feat: improve profile experience for end users

[neethika12]

Closes Sentinent-AI/Sentinent#23

User Impact

• Users can open a dedicated Profile page to view their personal account details in one place.
• Users can edit and save their profile information (name, role, organization, timezone, and bio).
• If profile data is slow or temporarily unavailable, users see clear feedback and can retry instead of getting stuck on a loading screen.
• Empty profile fields are shown with helpful fallback text so the page still feels complete and understandable.

What Was Validated

• Profile page rendering and edit behavior
• Retry/error behavior for delayed profile loading
• Profile service mapping for backend response formats
• Frontend unit tests passing in ChromeHeadless (69/69)