feat(recon): retain graph nodes across reingest

[gbxbgbl]

Summary

• Add a start-recon toggle for deleting the existing Neo4j graph, defaulting to retention.
• Stamp recon-populated graph nodes with first_seen, last_seen, first_seen_job_id, and last_seen_job_id using a per-run job context.
• Surface the new graph metadata in the graph UI and add focused Python/React coverage.

Type of Change

• Bug fix
• New feature
• Refactor (no behavior change)
• Documentation
• Test

Component(s)

• webapp (Next.js)
• recon-orchestrator (Python)
• agent (Python)
• kali-sandbox / MCP servers
• docs / wiki
• other: graph_db / recon

How to Test

1. docker compose build webapp
2. docker compose up -d webapp
3. Attempted: python -m pytest recon/tests/test_graph_delete_gate.py tests/test_graph_aux_seen_stamping.py tests/test_graph_job_context.py tests/test_graph_node_seen_stamping.py recon_orchestrator/test_parallel_partial_recon.py (blocked locally: Python has no pytest module installed)
4. Attempted: npx vitest run src/app/graph/components/ReconConfirmModal/ReconConfirmModal.test.tsx src/app/graph/components/NodeDetailsTable/NodeDetailsTable.test.tsx src/app/graph/components/NodeDetailsTable/nodeDetailsHelpers.test.ts (blocked locally: local webapp dependencies are not installed, so vitest/config could not resolve)

Checklist

• I have tested this change locally with docker compose
• I have not included real-world target data
• My commits follow Conventional Commits
• I have read and agree to the DISCLAIMER.md

Screenshots

N/A

Related Issues

N/A