beets: add simple http server to execute beets commands remotelly

[dyptan-io]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description:

Adds a new Docker Mod beets-httpshell that runs a lightweight Python 3 HTTP server (stdlib only, no pip dependencies) inside the beets container. It proxies HTTP POST requests to beet CLI commands — the URL path maps to the subcommand, and the JSON body provides arguments. For example, POST /import with body ["/downloads/album"] runs beet import /downloads/album.

Execution mode is controlled per-request via ?mode= query parameter (block, parallel, or queue).

Benefits of this PR and context:

The beets container lacks a built-in way to invoke commands remotely. This mod enables HTTP-based automation without SSH or docker exec, making it straightforward to integrate with tools like Lidarr, scripts, or other services in a Docker Compose stack.

• No extra dependencies — uses Python 3 already present in the image
• Dynamic command routing — any beet subcommand works, no hardcoded list
• Per-request execution modes for flexible concurrency control
• Simple JSON array format for arguments

How Has This Been Tested?

• Docker image builds successfully (docker build .)
• Single-layer image verified
• Python script syntax validated
• s6-overlay file structure and permissions verified against the mod template spec

Source / References:

• Beets CLI documentation
• LinuxServer.io Docker Mods
• LinuxServer.io beets container

[LinuxServer-CI]

PR build pushed to ghcr.io/linuxserver/mods:pull_request_1134

[LinuxServer-CI]

PR build pushed to ghcr.io/linuxserver/mods:pull_request_1134

[LinuxServer-CI]

PR build pushed to ghcr.io/linuxserver/mods:pull_request_1134

[aptalca]

Looks good to me, but please also remove Dockerfile.complex as it's not needed.

And please test the pushed mod ghcr.io/linuxserver/mods:pull_request_1134 and confirm it works as intended. Then we'll merge.

Thanks

[LinuxServer-CI]

PR build pushed to ghcr.io/linuxserver/mods:pull_request_1134

[dyptan-io]

Thank you for the review, @aptalca!
I removed the Dockerfile.complex and tested the mod installation from the PR build. All works as intended.