Polish topology evidence actions

[BadgerOps]

Summary

• Add Network Map topology evidence polish: historical evidence toggle, stale/current evidence status, and selected-evidence actions.
• Support promotion actions to use DNS evidence as a hostname, attach selected hosts to existing device identities, mark selected segments as expected network groups, and ignore noisy sources/observers for the current map view.
• Keep ignore behavior non-destructive and view-scoped; stored evidence is not removed or mutated.
• Expose current/stale evidence metadata from map relationships, including stale/removed timestamps, observation IDs, raw payload, and host hints for UI actions.
• Harden passive capture parsing for CDP address TLVs and DHCPv6 delegated prefixes, with additional LLDP/CDP/DHCPv6/mDNS synthetic pcap fixtures.
• Bump backend to 0.19.0, frontend to 0.18.0, and agent to 0.17.0.

Verification

• nix develop -c .venv/bin/python -m py_compile agent/grapheon_agent.py agent/tests/test_grapheon_agent.py backend/network/edges.py backend/tests/test_agents.py
• nix develop -c .venv/bin/python -m pytest agent/tests/test_grapheon_agent.py::test_parse_pcap_topology_evidence_extracts_lldp_and_cdp agent/tests/test_grapheon_agent.py::test_parse_pcap_topology_evidence_enriches_dns_nbns_and_discovery agent/tests/test_grapheon_agent.py::test_parse_pcap_topology_evidence_enriches_dhcpv4_dhcpv6_and_ra backend/tests/test_agents.py::TestAgentEnrollmentAndCheckIn::test_topology_evidence_checkin_feeds_evidence_api_and_map_layers
• nix develop -c npm --prefix frontend run build
• nix develop -c .venv/bin/python scripts/validate_versions.py
• nix develop -c .venv/bin/python -m pytest

Notes

• Full pytest passed with 418 passed, 1 skipped.
• Frontend build passes with the existing Vite large chunk warning.
• No *.pcap, *.pcapng, or *.cap artifacts were added.
• .pipeline/ contains local ship handoff files and remains ignored.