Switch to ffmpeg 7.1 + other fixes for audio streaming

[marcelveldt]

• Switch to Python Alpine base image including statically compiled ffmpeg 7.1, based on the foundation works by @chatziko in docker: use alpine3.21 with ffmpeg from mwader/static-ffmpeg #1877
• Various other optimizations to streaming in relation to ffmpeg
• More logging, especially on streaming errors
• Handle various paths in the code to recover from (un)expected issues during streaming

Back to Alpine instead of Debian mainly because its a lot more efficient in memory and file size.

While extended testing still identified two leftover issues but they are not related to the image change:

1. Librespot simply refuses to play some songs - at least they will now be displayed in the logs

2. Every once in a while ffmpeg crashes in the very last part of the track with this error 'Assertion best_input >= 0 failed at fftools/ffmpeg_filter' and then discard the last 5 or 6 seconds of the track - only seems to happen when the dynamic volume normalization is active (loudnorm filter)