feat(website): add a Docker page for the self-hosted browser version

Publish /download/docker/ so "Self-host it with Docker" no longer sends
visitors off-site to the developer README. The page covers what the
image contains, a four-step quick start with the repository compose
command and an image-only compose snippet, the environment variables
and port that matter, the published tag patterns with the update
command, what the browser version leaves out, and a seven-question FAQ.
It links to docker/README.md for the full reference, to the desktop vs
browser comparison and to the setup guides; the README links back.

The download hub gains a fourth card, the homepage and hub links point
at the page, the platform switcher shows a Docker card on the OS pages,
and the comparison page links both the page and the README. The page
emits SoftwareApplication / FAQPage / BreadcrumbList JSON-LD and is
covered by website-download-pages.test.mjs.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

CLAUDE.md

@@ -330,7 +330,7 @@ This is an Nx monorepo with the following structure:
 - **apps/electron-backend-e2e** - Playwright E2E tests against the Electron app
 - **apps/stalker-mock-server** - Mock Stalker/Ministra portal for dev and E2E
 - **apps/xtream-mock-server** - Mock Xtream Codes API for dev and E2E
-- **apps/website** - Astro + Tailwind landing page, blog (guides carry `faq:` frontmatter → FAQPage JSON-LD), per-OS download landing pages (`/download/`, `/download/{windows,macos,linux}/`) feature landing pages (`/features/`, registry in `src/lib/features.ts`) and comparison pages (`/compare/`, registry in `src/lib/comparisons.ts`, comparing IPTVnator's own options rather than other products); direct asset links are resolved at build time from the GitHub Releases API with a `package.json` fallback (`src/lib/downloads.ts`, see `apps/website/README.md`)
+- **apps/website** - Astro + Tailwind landing page, blog (guides carry `faq:` frontmatter → FAQPage JSON-LD), per-OS download landing pages (`/download/`, `/download/{windows,macos,linux}/`) plus the Docker page (`/download/docker/`) feature landing pages (`/features/`, registry in `src/lib/features.ts`) and comparison pages (`/compare/`, registry in `src/lib/comparisons.ts`, comparing IPTVnator's own options rather than other products); direct asset links are resolved at build time from the GitHub Releases API with a `package.json` fallback (`src/lib/downloads.ts`, see `apps/website/README.md`)
 - **libs/** - Shared libraries:
     - **epg/data-access** - EPG services, runtime bridge, program normalization
     - **m3u-state** - NgRx state management for M3U playlists