Move the app catalog into catalog/ and start each one in CI

[v0l]

Extracts the example managed-app composes out of docs/managed-app-examples.md into a flat catalog/ directory, and adds CI that starts each one.

• catalog/*.yaml — 7 standalone documents (blossom-server, buzz, haven, nostr-rs-relay, pyramid, route96, strfry). The doc keeps the grammar notes and now links the files instead of carrying 350 lines of fenced YAML.
• scripts/app-catalog-test.sh — renders one document with compose-to-docker, applies the volume chowns the renderer prints (docker has no fsGroup), starts the stack, and fails on a service that exits non-zero, restarts, or an ingress port that never answers. HOST_PORT_OFFSET shifts published ports for local runs.
• .github/workflows/app-catalog.yml — validates every document, then one matrix job per file, discovered from the directory so adding a .yaml is enough to get it tested. Weekly cron because most entries pin a mutable tag.
• lnvps_operator test catalog_documents_map_to_k8s now reads catalog/ instead of parsing markdown fences (lnvps_operator/src/app_deployments.rs:3191).

Validation checks the document's grammar; it cannot know whether a third-party image can start under the hardening the operator applies. This runs them.

All 7 pass locally on this branch. cargo test --workspace --exclude lnvps_e2e green at 50d05ff (lnvps_e2e needs the live stack, not started here); clippy unchanged on the touched file.

Channel: 721a8a6c-c36c-5fa1-ae07-822ddc8567c5