Fix: Chromecast Casting Not Playing

[dude-stash]

Description

Casting to a Chromecast connects, but the TV never plays anything. There are two reasons:

1. Stash sends the TV the stream the browser is playing. It is labelled video/mp4 even for MKV, AVI or WMV files, which the TV can't play.
2. The stream URL points at localhost, which for the TV is the TV itself.

This keeps @silvermine/videojs-chromecast unmodified and fixes casting around it:

• The server now reports its LAN addresses in systemStatus.localIPs.
• Before each load, the plugin's modifyLoadRequestFn option swaps in a stream the TV can play: the direct stream for H.264 or H.265 with AAC or MP3 in MP4, otherwise HLS. localhost is replaced with the LAN address. Signed URLs keep working.
• Seeking a transcoded scene while casting goes to the TV, because live.ts steps aside while the Chromecast tech is active.
• The Cast SDK is loaded once per page, so casting keeps going while you browse between scenes.

The @silvermine/videojs-chromecast plugin hasn't been maintained since 2024, so instead of patching it, ScenePlayer/chromecast-tech.ts registers a subclass of its tech. It copes with a cast that outlives the previous player (no source or session manager yet, events after disposal), which was the plugin's open issue #96, and implements loop, setLoop and seeking.

It also defines setSource itself, because Video.js only calls it on a tech whose own prototype has it. This makes Chromecast work with Video.js 7 without patching the package.

Only the last three commits are specific to the Video.js 7 player (ScenePlayer.tsx, live.ts and the tech subclass).

The first two stay needed after a move to Video.js 10, because they don't touch the player: localIPs on the server, and utils/castMedia.ts, which picks the stream and address.

Related Issue

Fixes #4136. Replaces #7220.

Testing

Manual testing with a Chromecast with Google TV, an older Chromecast and a Google Nest Hub, from Chrome on macOS:

• H.264 and H.265 MP4 plays directly. MKV, AVI and WMV play through HLS.
• Seeking while casting, including transcoded scenes.
• Opening another scene while casting, and going to the scenes list and back.
• The queue moving on to the next scene when one ends.

Automated checks:

• go build ./... and go test ./pkg/utils/ ./internal/manager/
• golangci-lint on the changed Go packages
• pnpm run validate (biome, tsc, format)

Screenshots

No visual changes.

Checklist

• I have read and understood the Contributing document.
• I have read and understood the AI Usage Policy document.
• I have made corresponding changes to the documentation (if applicable).

AI Usage Disclosure

• I have used AI tools to assist with this pull request, and I have disclosed the tools and how I used them below.

I used Claude Code to investigate the problem, write the code and commit messages, and draft this description. I directed the work, reviewed every commit and did the manual testing on my own devices.

Additional Context

The commits are meant to be reviewed one at a time.

[dude-stash]

@Gykes I found another way to fix casting on vjs 7 without patching the silvermine chromecast plugin.

The first two commits are what makes stash send a valid url to chromecast instead of localhost, which is also needed for vis 10 anyway. But this PR makes chromecast completely usable on vjs 7.