feat(http): add --otlp-tracing-filter to exclude HTTP paths from Open…

[bastiansmn]

…Telemetry tracing

Health checks, metrics scrapes, and other probe endpoints generate noise in OpenTelemetry traces without revealing meaningful traffic patterns. The new --otlp-tracing-filter flag (repeatable, or comma-separated via env var) accepts a list of exact HTTP paths that should produce no OTEL span. Internally OtelAxumLayer.filter() is used so excluded paths emit tracing::Span::none() with zero overhead on the hot path.

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Fixes # (issue)

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