Add DNSDumpster-like inventory and report sections

[Swapshadow]

Motivation

• Provide a DNSDumpster-style consolidated view from OpenEASM scan data so reports (JSON/HTML/PDF/Excel) expose System Locations, Hosting/Networks, Services/Banners, A/MX/NS/TXT records and a detailed Host Inventory like DNSDumpster.
• Treat HTTP/HTTPS/TLS fingerprinting as the primary source for web services while keeping Nmap as a complementary annex.

Description

• Added a new service backend/app/services/dnsdumpster_like_inventory.py that builds audit["dnsdumpster_like"] by merging DNS, subdomains, ASN (Team Cymru), HTTP/HTTPS fingerprints, TLS certificate parsing, local RevIP counts, guardrail logs and complementary Nmap services.
• Integrated the generator into the audit flow in backend/app/main.py so dnsdumpster_like is created after DNS, mail, subdomains, IP inventory and service scans and included in the API/JSON summary.
• Extended report generators to include DNSDumpster-like sections: updated backend/app/reports/pdf_report.py (new PDF layout and DNSDumpster sections with Nmap/CVE in annex), backend/app/reports/html_report.py (DNSDumpster UI, filterable A-records table, badges, expandable host details and client-side filter JS) and backend/app/reports/excel_report.py (new workbook sheets and enriched columns for A/MX/NS/TXT and Host Inventory).
• Added TLS DER parsing with cryptography fallback, richer HTTP fingerprinting logic, technology detection from headers/HTML and conservative ASN enrichment, and set default OPENEASM_NMAP_TOP_PORTS=1000.

Testing

• python3 -m compileall backend/app — succeeded (module-level compile check of the modified codebase completed).
• python3 -m pip install -r backend/requirements.txt — failed due to environment package index/proxy returning 403 Forbidden, preventing installation of runtime dependencies (so dynamic integration tests could not be executed in this container).
• Smoke attempt to run the DNSDumpster-like builder against oehc.corsica (via a small script invoking the new module) failed with ModuleNotFoundError: No module named 'dns' because dependencies were not installed after the pip failure.

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Codex Task