Add adaptive packet loss handling

PROGRESS.md

@@ -25,13 +25,15 @@ verified on an iPhone 16 Pro Max with a two-channel AVAudioEngine input and dist
 samples; the managed Apple binding requires native use of its otherwise-unmapped stereo polar
 pattern constant.
 
-SQLite schema v3 persists channel DRED settings and migrates existing v1/v2 databases with DRED
-disabled until explicitly enabled.
+SQLite schema v4 persists DRED and the channel packet-loss mode. Manual loss remains the default;
+automatic Fast/Balanced/Stable modes measure each sender's authenticated UDP uplink at the server,
+cap the applied Opus hint at 30%, and feed it back over TLS.
 
 ## Release gates
 
 - Run real multi-person calls on Windows, macOS, and physical iOS hardware, including adaptive
-  20/40/60 ms buffering, duration-aware DRED/FEC, and mismatched input/output endpoints.
+  20/40/60 ms buffering, duration-aware DRED/FEC, automatic packet-loss feedback, and mismatched
+  input/output endpoints.
 - Complete NVDA and VoiceOver navigation/announcement passes.
 - Exercise iOS background/lock, interruption, Bluetooth, route-change, ReplayKit, and iOS 27
   ScreenCaptureKit paths on devices. Complete extended mono/stereo/voice-chat switching while