Write tutorial 'Events and Logs' (evm/tutorials/intermediate/events-and-logs)

**Page:** `evm/tutorials/intermediate/events-and-logs.mdx`

**Context:** Siblings `send-receive-hbar`, `verify-hashscan`, `json-rpc-connections/` are written.

**Scope:** Emitting events in Solidity, querying logs via JSON-RPC + Mirror Node, filters.

### 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