feat(source): add source@v1 cli

[rudyberends]

This PR adds a source@v1 reference implementation to sendspin-cli.

You can now run source input in two modes:

• sendspin source run (source-only client)
• sendspin daemon --source (player + source in one process)

The implementation supports line-in capture and synthetic sine input, source state reporting, source start/stop control, optional source control hooks, and reconnect behavior aligned with daemon operation.

What’s included

• Added shared source runtime modules:
  • sendspin/source_stream.py
  • sendspin/source_utils.py
• Extended CLI:
  • new source run command
  • daemon source flags (--source-*)
  • input device listing (--list-input-devices)
• Integrated source role into daemon mode:
  • advertises source@v1 support in hello when enabled
  • handles source commands and input stream format requests
  • uses the same source streaming path as source run
• Added persistent daemon settings for source options and source hooks
• Updated README with source usage, options, and examples

Notes

• Source control hooks are optional:
  • --source-hook-play
  • --source-hook-pause
  • --source-hook-next
  • --source-hook-previous
  • --source-hook-activate
  • --source-hook-deactivate
• Sine input is intended as a lightweight test/debug path when no capture device is available.

[balloob]

Hey, thanks for the PR!

Quick review: See some inline imports still hanging around.

We still need to finalize the source spec, but when we do this will be a great addition!

Are you hanging out in the sendspin channels on the Music Assistant discord?

[rudyberends]

Thanks for the feedback. I removed the remaining inline imports in daemon.py and moved them to module-level imports in commit 61938c8.