Cutover: soak-test, flip push target test→live, switch public player HLS/FLV→Icecast

[anneoneone]

Goal

Cut over from NMS to Icecast: soak-test, flip the push target, switch the public player — keeping NMS warm for fast rollback (Phase 3 of #164).

Tasks

• Soak-test a full-length show on /test on a real phone over cellular while NMS still serves production.
• Flip the ffmpeg push target test→live and switch the frontend player from HLS/FLV to the Icecast mount. Touch frontend/src/config.ts (replace the HLS/FLV URLs — currently https://stream.moafunk.de/live/stream-io/index.m3u8 + .flv), frontend/src/streamDetector.ts / frontend/src/main.ts (the HLS HEAD-poll every 8s becomes a /status-json.xsl / mount probe), and frontend/src/player.ts (drop flv.js → native <audio>).
• Keep NMS warm for fast rollback for a few shows.

Acceptance

A real show runs end-to-end on Icecast (desktop + iOS), recording lands in R2 verified, NMS can be re-enabled in <5 min if needed.

Depends on

All Phase-2 tickets (#164).

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Parent: #164 (Phase 3).