feat: pentest feature improvements — streaming, pause/resume, encryption, browser tool, reports, docs

- True SSE streaming via broadcast channels (DashMap per session)
- Session pause/resume with watch channels + dashboard buttons
- AES-256-GCM credential encryption at rest (PENTEST_ENCRYPTION_KEY)
- Concurrency limiter (Semaphore, max 5 sessions, 429 on overflow)
- Browser tool: headless Chrome CDP automation (navigate, click, fill, screenshot, evaluate)
- Report code-level correlation: SAST findings, code graph, SBOM linked per DAST finding
- Split html.rs (1919 LOC) into html/ module directory (8 files)
- Wizard: target/repo dropdowns from existing data, SSH key display, close button on all steps
- Auth: auto-register with optional registration URL (Playwright discovery), plus-addressing email, IMAP overrides
- Attack chain: tool input/output in detail panel, running node pulse animation
- Architecture docs with Mermaid diagrams + 8 screenshots

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Cargo.toml

@@ -30,3 +30,6 @@ uuid = { version = "1", features = ["v4", "serde"] }
 secrecy = { version = "0.10", features = ["serde"] }
 regex = "1"
 zip = { version = "2", features = ["aes-crypto", "deflate"] }
+dashmap = "6"
+tokio-stream = { version = "0.1", features = ["sync"] }
+aes-gcm = "0.10"