docs: CHANGELOG + GitHub Pages landing + repo metadata polish

[hculap]

Why

Two things missing from the repo:

1. A single source of truth for what shipped when (`CHANGELOG.md` — GH Release notes scatter across 9 releases now)
2. A user-facing landing page (`https://hculap.github.io/emodul/\`) that's friendlier than the README for non-developer audiences (Polish heating users finding us via search, Reddit / HA community drive-by clicks)

What

• `CHANGELOG.md` — Keep-a-Changelog format, 0.1.0 → 0.1.9. Linked from README header.
• `docs/` — Jekyll cayman theme (zero-build, supported natively by GH Pages). `docs/index.md` is a Polish-first landing covering: what emodul is, install snippet, three runtime paths, example PL queries, security notes, vs-HA-integration comparison. Ready to ship as soon as you enable Pages in Settings.
• README header: PyPI badge + quick-link strip (landing · changelog · PyPI · AGENT.md)
• Repo metadata (applied separately via `gh repo edit`):
  • Description rewritten to lead with MCP integration
  • Homepage URL → https://hculap.github.io/emodul/
  • Topics: dropped 5 low-signal tags, added `mcp`, `mcp-server`, `model-context-protocol`, `claude-desktop`, `cursor-ide`

After merge

You need to enable Pages once (30s):

1. https://github.com/hculap/emodul/settings/pages
2. Source: Deploy from a branch → Branch: `main` → Folder: `/docs`
3. Save. GitHub builds the site, URL appears at the top of that settings page.

That's it. Subsequent updates just push to `main` and the site auto-rebuilds in ~1 min.

No code changes

Pure docs / metadata PR. No version bump, no PyPI publish, no breaking changes.