Write 'Migration Checklist' (evm/differences/checklist)

**Page:** `evm/differences/checklist.mdx`

**Context:** Rich written siblings (`key-differences-overview`, `accounts-and-keys`, `hbar-decimals`, `json-rpc-differences`, `native-token-transfers`, `tooling-compatibility`, `native-devs/`).

**Scope:** Consolidated step-by-step migration checklist that links each existing migration page. Mostly structured checklist referencing siblings — low authoring lift.

### 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