Refactor: hardcoded 500ms threshold in TempoTraceAdapter

[Mar10-Labs]

The polling integrity check uses a hardcoded 500ms value to detect if the slow span batch has been flushed. Works for the demo but misses subtle latency regressions.\n\njava\nboolean complete = tree.spans().stream()\n .anyMatch(s -> s.durationMs() > 500); // hardcoded\n\n\nGoal: make threshold configurable via application.properties and investigate a statistical approach instead of a fixed value.