Contact form wired to email + DB

[MrImmortal09]

Context

/contact currently has a non-functional form. Wire it to persist messages and email technicalclub@iiitl.ac.in.

Acceptance criteria

• ContactMessage table with name, email, message, createdAt, handledBy, handledAt
• Submissions also email the superadmin
• Admin inbox at /admin/contact with "Mark handled" button
• Rate limit: 3 submissions per IP per hour
• Honeypot field to filter bots

Depends on #7, #22.