fix(audio): add missing MainMediaAudioBuffer sources

AndroidMediaSink, AirPlayPersistence and CarPlayHostActivity referenced
MainMediaAudioBuffer, but its sources were absent from the tree, so
:shared:compileDebugKotlin could not resolve the class.

Restored from the leftover compiled class in shared/build: duration range
100..1000 ms snapped to 100 ms steps (100 ms default), PCM16 AudioTrack
capacity kept above the system minimum, and main-media stream types
100/102 selected only for the "media" audio category.

Bump to 1.2.4

Bump to 1.2.3

chore: bump version code

...?

feat: add signed release workflow for tags