fix(android): pass PROTOCOL_DNS_SD so mDNS registration works

Android 16 added NsdManager.checkProtocol(): registerService with protocol
0 threw IllegalArgumentException: Unsupported protocol — silently, since
the old code swallowed the exception into a dead reflection fallback and
start() overwrote the failure status with the Listening line. mDNS never
actually advertised (the Phase 8 session streamed via --peer, masking it).

Also advertise after the listening status so a registration failure stays
visible, and log the exception and the registration success.

Validated live on the Fairphone 6: the desktop --discover lists the phone
and a full --send session decodes (in-band SPS 320x240 -> 2496x1040) and
renders.

docs/PHASES.md

@@ -114,6 +114,13 @@ existing signaling + RTP protocol; no C++ changes.
       depacketizer — 25 tests green)
 - [x] 8.3 Signaling + NSD validated on device (offer → answer over the
       network; mDNS registration via the API-36 RegistrationListener)
+      — **correction 2026-09-10**: registration had in fact never
+      succeeded (registerService passed protocol `0`, which API 36
+      rejects with "Unsupported protocol"; the swallowed failure was
+      hidden behind the "Listening…" status). Fixed with
+      `PROTOCOL_DNS_SD` + real on-device validation: desktop
+      `--discover` lists the phone and a live `--send` session
+      decodes and renders.
 - [x] 8.4 MediaCodec decode + Surface render validated on device (in-band
       SPS sizing, letterbox fit)
 - [x] 8.5 End-to-end on a Fairphone 6 (Android 16): streaming, letterboxed