docs: add enterprise evaluation guide

[peg]

Summary

• Adds security-review-oriented evaluation docs covering data flow, files touched, safe pilot workflow, proof artifacts, cleanup, and limitations.
• Adds self-hosting guidance for snare serve, Docker Compose, Cloudflare Worker deployments, reverse proxies, backups, and upgrades.
• Adds SIEM integration guides for generic webhooks, Splunk, Datadog, and Microsoft Sentinel.
• Links the new docs from README/SECURITY/ARCHITECTURE and adds snare serve --help with test coverage.

Tests

• git diff --check origin/main...HEAD
• go build ./...
• go vet ./...
• go test ./... -count=1
• go test ./... -race -count=1
• (cd worker && npm ci && npm test)
• SNARE_DASHBOARD_TOKEN=0123456789abcdef0123456789abcdef SNARE_PORT=18080 docker compose config --quiet
• docker compose -p snare-docs-smoke up -d --build + /health smoke test
• go run golang.org/x/vuln/cmd/govulncheck@latest ./...
• go run honnef.co/go/tools/cmd/staticcheck@latest ./...
• Markdown relative-link check for repository docs