[BUG] Contact form shows generic error alert instead of meaningful feedback

[HKratos2001]

Description

When the contact form submission fails (for any reason — duplicate email, missing fields, server error), the user sees a generic `alert("Form submit encountered an error, check console")`. This provides no actionable information.

Root Cause

Frontend (`/pages/patient/contactForm.vue`, lines 796-800):
```javascript
catch (e) {
console.log(e.statusMessage + ":");
console.log(e.data);
alert("Form submit encountered an error, check console");
}
// TODO make better than bandaid
```

Backend (`/server/api/contactForm/form.post.ts`, lines 75-77):
Uses `handlePrismaError(e)` which returns structured errors, but the frontend ignores the error details.

Fix

1. Parse `e.data` and `e.statusMessage` from the server response
2. Display specific error messages inline next to the relevant fields
3. Common errors to handle:
   • Duplicate email → "An account with this email already exists"
   • Missing required field → highlight the field
   • Server error → "Something went wrong, please try again"
4. Remove the `alert()` and `console.log` approach

Related

• [BUG] Duplicate email signup shows generic error instead of helpful message #170 (duplicate email specifically)
• [Task] contact form errors #100 (same issue, older)

Acceptance Criteria

• Error messages are shown inline near the relevant form field
• No generic alerts or console-only errors
• Each error type has a user-friendly message