chore: clean up contrib/, fix upstream refs, retire lgtm.yml

Remove stale contrib/ files superseded by current tooling:
- contrib/airsonic.service (superseded by install/systemd/)
- contrib/airsonic-systemd-env (superseded by installer override files)
- contrib/deploy.sh (Tomcat-based, not applicable to standalone WAR)
- contrib/release.md (manual process replaced by GitHub Actions)

Fix upstream references in install/:
- install/docker/Dockerfile: update LABEL url to litebito/airsonic-pulse
- install/compose/docker-compose.hsqldb.yaml: rename service/container,
  update image to ghcr.io/litebito/airsonic-pulse
- install/compose/docker-compose.postgres.yaml: update image reference

Fix upstream reference in .github/CONTRIBUTING.md (line 5)

Retire lgtm.yml: LGTM was shut down November 2022; CodeQL workflow
(any_codeql_scan.yml) is the current replacement.

Fix .github/workflows/any_trivy_scan missing .yml extension so GitHub
Actions recognises the workflow file.

Update contrib/i18n_fix_encoding.go: replace deprecated io/ioutil with
io.ReadAll and os.WriteFile (Go 1.16+).

Fix contrib/library_autoupdater.sh: correct misleading comment
("10 minutes") to match actual sleep duration (3600s = 60 minutes).

.github/CONTRIBUTING.md

@@ -7,5 +7,5 @@ litebito/airsonic-pulse development is a community project, and contributions ar
   2.  **No Breakage** New features or changes to existing ones must not degrade the user experience. This means do not introduce bugs, remove functionality, or make large changes to existing themes/UI without prior discussion in an Issue.
   3.  **Coding standards** Language best-practices should be followed, comment generously, and avoid "clever" algorithms. Refactoring existing messes is great, but watch out for breakage.
   4.  **Be bold!** Without contributions, this project will vanish. If you just want to help out, try [submiting a patch](https://github.com/litebito/airsonic-pulse/issues?q=is%3Aissue+is%3Aopen+label%3Apatches-welcome) for an open Issue.
-  5.  **Stay relevant** Issues or commentary that is off-topic or tangential to kagemomiji/airsonic-advanced development is subject to moderation. Questions should be focused on improving documentation to solve a problem. Visit [GitHub Discussions](https://github.com/litebito/airsonic-pulse/discussions)
+  5.  **Stay relevant** Issues or commentary that is off-topic or tangential to litebito/airsonic-pulse development is subject to moderation. Questions should be focused on improving documentation to solve a problem. Visit [GitHub Discussions](https://github.com/litebito/airsonic-pulse/discussions)