Reduce executive TCP retransmit noise from minimal flows

[rchac]

This draft PR addresses issue #1033 by reducing retransmit noise in executive / queue-dynamics summary heatmaps caused by very small TCP samples.

What Changed

• Added a shared executive retransmit confidence gate in temporal_heatmap.rs.
• Executive retransmit samples now require:
  • tcp_packets >= 100
  • retransmits >= 2
• Samples below that confidence floor are suppressed as None instead of being colored as 0% or a noisy retransmit percentage.

Scope

This change applies only to summary heatmap paths:

• circuit/global executive heatmaps
• site heatmaps
• ASN heatmaps

Detailed circuit and per-flow retransmit drill-down data is unchanged.

Implementation Details

• Circuit/global summary heatmap gating is applied in tracking_data.rs.
• Site heatmap gating is applied in network_json.rs.
• ASN heatmap gating is applied in asn_heatmap.rs.

Tests

Added focused coverage for the three backend summary paths:

• low-confidence circuit/global retransmit samples are suppressed
• qualified circuit/global retransmit samples still color
• low-confidence site retransmit samples are suppressed
• qualified site retransmit samples still color
• low-confidence ASN retransmit samples are suppressed
• qualified ASN retransmit samples still color

Validation

• cargo fmt --all
• cargo test -p lqos_utils temporal_heatmap -- --nocapture
• cargo test -p lqos_config network_json::test::site_heatmap -- --nocapture
• cargo test -p lqosd throughput_tracker::tracking_data::tests::circuit_and_global_heatmaps -- --nocapture
• cargo test -p lqosd throughput_tracker::flow_data::asn_heatmap::tests -- --nocapture
• cargo check -p lqos_config -p lqosd
• cargo clippy -p lqos_config --all-targets -- -D warnings
• cargo clippy -p lqosd --all-targets -- -D warnings

Follow-Up Not In This PR

• Exclusion-list semantics for retransmit summaries
• Richer retransmit tooltip/sample metadata in the executive heatmap payload