Wire up Contact page frontend to real backend API

[yusuftomilola]

Description:
Replace the simulated setTimeout in the Contact page's handleSubmit with a real API call to POST /contact using apiClient. Add proper error handling with toast notifications. Keep all form validation and UI unchanged.

Acceptance Criteria:

• handleSubmit calls apiClient.post("/contact", { ... })
• Sends: fullName, email, phone (optional), company (optional), subject, message
• Shows toast error on failure
• Shows success view on successful submission
• Loading state shown during API call
• No changes to form validation or UI layout

File(s): frontend/app/contact/page.tsx

[arya23923]

May I be assigned this issue?