feat(template): add CineDock v3 template

[cinedock-release]

What changed

• Add CineDock 4.1.6 to the Portainer v3 template catalog.
• Add a linked Compose stack using the official multi-architecture GHCR image.
• Persist /config in a named volume and publish web port 8945 by default.
• Expose only the optional published-port and TMDB API key variables.

Closes #267.

Why

CineDock provides a cinematic, television-first interface for an existing Emby, Jellyfin or Plex server. The template keeps media and authentication owned by that existing server and does not request GPU, media, Docker socket, privileged, or host-path access.

Validation

• Portainer's exact orrosenblatt/validate-json-action:latest PR validator passed against schema.json and templates.json.
• docker compose config --quiet passed for the linked stack.
• The linked stack started successfully and reached healthy.
• / returned HTTP 200.
• /tvapp-version.json returned {build:4.1.6}.
• Runtime inspection confirmed one named volume mounted at /config and only port 8945 published.
• The 4.1.6 image manifest contains linux/amd64 and linux/arm64.

User impact

Users can deploy CineDock from Portainer's v3 catalog, open the published web port, and connect their existing media server through CineDock's setup wizard.