android: add in-app high-resolution AirPods mic stream

[IvanChanPing]

Summary

• routes AACP 0x58 microphone SDUs without blocking control traffic
• parses bounded AAC-ELD access units and decodes them with Android MediaCodec
• exposes off-main, app-scoped PCM through the bound AirPods service
• sends the verified start/stop control packets, restores conversational-awareness state, and cleans up on disconnect
• expands the socket buffer to 4096 bytes and excludes audio packets from broadcasts, notification refreshes, and packet logs

This implements the no-root, in-app transport/decoder portion of #720. It does not claim to publish a system microphone for other apps.

Verification

• ANDROID_HOME=/opt/android-sdk ./gradlew :app:testFossDebugUnitTest
• parser tests cover multiple access units, truncated tails, non-audio subtype, and short packets
• compile/unit-test verified only; real AirPods and on-device AAC-ELD decode remain unverified

Also implements the Android AACP-microphone slice identified in #713.