[SUP-002] Support: Contact Us form & support ticket creation

## Overview
Build a Contact Us form that creates a support ticket, optionally linked to an order or return, and routes it to the support team.

## Acceptance Criteria
- [ ] Route: `/contact` — contact form page
- [ ] Fields: name (pre-filled if logged in), email, subject, message, optional order ID, optional attachment
- [ ] Subject dropdown: Order Issue, Return & Refund, Account Help, Payment Issue, Product Question, Other
- [ ] `POST /api/support/tickets` — creates a ticket with a unique ticket ID
- [ ] Auto-reply email sent to customer confirming ticket receipt (via #19)
- [ ] If user is logged in and references an order (#14) or RMA (#18), ticket is auto-linked
- [ ] Ticket status page: `/contact/ticket/:ticketId` (accessible without login via email link)
- [ ] Basic spam protection (honeypot field + rate limiting)

## Depends On
- #5 AUTH-001 — pre-fill user data for logged-in users (soft dependency — form works without auth)
- #19 NOTIF-001 — auto-reply email requires notification service