feat: full quality tiers + slider UI + key-change warning on Android

1. Wire protocol: add Opus 32k/48k/64k (CodecId 6/7/8) + STUDIO
   profiles with is_opus() helper. Opus enc/dec accept all Opus variants.

2. JNI bridge: expand profile_from_int to 7 levels (0-6) mapping to
   GOOD, DEGRADED, CATASTROPHIC, Codec2_3200, STUDIO_32K/48K/64K.

3. Settings UI: replace radio buttons with Material3 Slider — 7 stops
   from Studio 64k (green) to Codec2 1.2k (dark red), matching desktop.

4. Key-change warning: AlertDialog on connect when server fingerprint
   has changed. Shows old vs new fingerprint, Accept New Key or Cancel.
   Accepting saves the new fingerprint and proceeds with the call.

5. Engine recv: handle studio codec IDs in auto-switch path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-codec/src/opus_dec.rs

@@ -79,7 +79,7 @@ impl AudioDecoder for OpusDecoder {
 
     fn set_profile(&mut self, profile: QualityProfile) -> Result<(), CodecError> {
         match profile.codec {
-            CodecId::Opus24k | CodecId::Opus16k | CodecId::Opus6k => {
+            c if c.is_opus() => {
                 self.codec_id = profile.codec;
                 self.frame_duration_ms = profile.frame_duration_ms;
                 Ok(())