scrypted: only warn about dropped frames when drops exceed 25% of target rate

ffmpeg's fps filter sometimes emits timestamp-clumped pairs at low
rates; the single-flight POST guard correctly drops the second one
and we logged a "raise frame_interval_ms" warning for every such
event. At 500ms interval (2 fps target) a single drop produced a
0.6 fps warning even though we were still painting the requested
rate.

Suppress the message unless drops exceed a quarter of the configured
rate. Above that threshold there's real backpressure worth knowing
about; below it's just decimation noise.

0 files changed, 0 insertions, 0 deletions