feat: add Midnight dApp security checklist tutorial (#320)

[aglichandrap]

Summary

Closes #320

Adds a comprehensive pre-deployment security checklist tutorial for Midnight dApps. This is a Tier 2 (Medium) submission targeting $500-$700 in NIGHT tokens.

Deliverables

Written tutorial (~3,000 words) covering all 7 required security checks:

1. disclose() audit — Identifying secret leaks in Compact contracts
2. ownPublicKey() usage review — Known vulnerability patterns and proper authentication
3. Replay protection verification — Nonce and nullifier implementation
4. Exported ledger field review — Correct visibility and typing
5. Witness implementation correctness — Input validation and edge cases
6. Version compatibility confirmation — SDK, compiler, and proof server alignment
7. Proof generation testing on testnet — Comprehensive testing strategy

Format

• Practical, code-heavy tutorial with real Compact and TypeScript examples
• Each section includes audit steps, code examples, and common pitfalls
• Pre-deployment checklist summary table for quick reference
• Follows Midnight technical style guide

Publishing

Tutorial included in tutorials/security-checklist.md. Ready for publication on Dev.to or Midnight docs.

Checklist

• Written tutorial (2,500-3,500 words)
• Code examples tested and functional
• Follows Midnight technical style guide
• Covers all 7 required security checks
• Published on Dev.to (pending review)
• Shared on X/LinkedIn with #MidnightforDevs (pending publication)

[CLAassistant]

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