Write tutorial 'Create a Simple NFT' (evm/tutorials/beginner/simple-nft)

**Page:** `evm/tutorials/beginner/simple-nft.mdx`

**Context:** Siblings `connect-metamask`, `your-first-token` are written.

**Scope:** Deploy a simple ERC-721 collection step by step.

⚠️ **Clarify:** scope vs `evm/tutorials/hedera/nft-solidity` — state clearly whether this is the ERC-721 path or HTS path.

### Acceptance criteria
- [ ] Replace the placeholder template with real content
- [ ] Remove `hidden: true` from the frontmatter
- [ ] Follow the style guide: **markdown tables only** (no HTML ``), and avoid AI-tell phrasing (no em-dashes, "delve", "leverage", "not just X but Y")
- [ ] Add working cross-links to related pages
- [ ] Confirm any code samples run on testnet