Bound live-stream latency drift with periodic live-edge resync

Over hours the wall drifted ~15s behind real-time: the Pi decodes a hair
slower than real-time, and since RTSP-over-TCP delivers every byte, that
small deficit buffers up instead of being dropped — and a live stream
can't be seeked back to the live edge.

Add player.resync_seconds (0 = off): the daemon reconnects each stream to
the live edge on that interval via mpv loadfile-replace over IPC, cycling
one tile at a time so only a single tile ever blips. Reusing the running
mpv process means no window teardown. At 600s this caps drift to a couple
seconds. config.example.yaml ships it at 600; README documents the knob
and the "also lighten decode load" caveat.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

config.example.yaml

@@ -22,6 +22,9 @@ player:
   max_fps: 0                   # cap rendered fps (0 = uncapped); trims render load
   audio: false                 # streams are muted by default (saves CPU too);
                                # set true to decode and play camera audio
+  resync_seconds: 600          # reconnect each stream to the live edge on this
+                               # interval (staggered) so latency can't slowly
+                               # drift; 0 = off. 600 keeps drift to a few sec.
   restart_backoff_seconds: 3
   extra_args: []