feat: add TCP connection latency (RTT) measurement

[LeandroPG19]

Summary

Implements latency (RTT) measurement for TCP connections as requested in #845.

How it works

Measures the Round-Trip Time from the TCP handshake: when a SYN packet is captured, its pcap timestamp is stored. When the matching SYN-ACK arrives, the difference between the two timestamps gives the RTT. The latency is then displayed in milliseconds on the connection details page.

Changes

File	What
src/networking/parse_packets.rs	Track pending SYN timestamps in a HashMap. On SYN-ACK, compute RTT via compute_rtt() helper. Clone LaxPacketHeaders to access TCP flags after analyze_headers.
src/networking/manage_packets.rs	modify_or_insert_in_map accepts latency: Option<Duration> and stores it on InfoAddressPortPair.
src/networking/types/info_address_port_pair.rs	New latency: Option<Duration> field. refresh() preserves existing latency unless a new one arrives.
src/gui/pages/connection_details_page.rs	Display "Latency: X.X ms" when available.
src/translations/translations_5.rs	latency_translation() in 16 languages.

Tests

9 new tests added (180 total, all passing):

• test_compute_rtt_basic — simple RTT within same second
• test_compute_rtt_crossing_second — RTT crossing second boundary
• test_compute_rtt_large_gap — multi-second RTT
• test_compute_rtt_zero — zero RTT (same timestamp)
• test_compute_rtt_negative_returns_none — inverted timestamps → None
• test_compute_rtt_display_ms — display format "25.0 ms"
• test_latency_default_is_none — default is None
• test_latency_refresh_overwrites_when_some — refresh overwrites when new value present
• test_latency_refresh_preserves_when_other_none — refresh preserves when no new value

running 180 tests
test result: ok. 180 passed; 0 failed; 0 ignored; 0 measured

Closes #845

[GyulyVGC]

Thanks but this is already being implemented with ICMP pings in #1194