feat: pure Dioxus attack chain visualization, PDF report redesign, and orchestrator data fixes

- Replace vis-network JS graph with pure RSX attack chain component
  featuring KPI header, phase rail, expandable accordion with tool
  category chips, risk scores, and findings pills
- Redesign pentest report as professional PDF-first document with
  cover page, table of contents, severity bar chart, phased attack
  chain timeline, and print-friendly light theme
- Fix orchestrator to populate findings_produced, risk_score, and
  llm_reasoning on attack chain nodes
- Capture LLM reasoning text alongside tool calls in LlmResponse enum
- Add session-level KPI fallback for older pentest data
- Remove attack-chain-viz.js and prototype files
- Add encrypted ZIP report export endpoint with password protection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -29,3 +29,4 @@ hex = "0.4"
 uuid = { version = "1", features = ["v4", "serde"] }
 secrecy = { version = "0.10", features = ["serde"] }
 regex = "1"
+zip = { version = "2", features = ["aes-crypto", "deflate"] }