Add ScanMalware expansion module

[jonaslejon]

New expansion + hover module: ScanMalware

Adds misp_modules/modules/expansion/scanmalware.py, enriching domain, hostname, url,
ip-src, ip-dst and domain|ip attributes from the public
ScanMalware API, returning misp_standard results built with PyMISP.

No API key. The API is anonymous and a key only raises the rate limit
(600 req/min anonymous), so moduleconfig is ["api_url", "max_results"] and
requirements is empty. The module works on a fresh install with nothing configured.

Behaviour

• A domain or hostname is queried against two different populations, not one.
  /api/v1/ct/dns/ returns subdomains seen in Certificate Transparency DNS records;
  /api/v1/hosts/ returns hosts a browser actually resolved and requested while rendering
  pages on that domain. The second is what certificate-based sources structurally cannot
  see: dev and staging hosts that hold no certificate. Querying only the first loses them.
• A URL returns the most recent completed sandbox scan of its host, with the verdict, a
  link to the full report, and the IPs contacted while rendering.
• An IP returns the URLs in the public archive that resolved to that address.
• Results are capped, and the cap says so. max_results defaults to 200. Unbounded,
  cloudflare.com returns 1,207 attributes, which makes an event unusable. The cap and
  any truncation the API itself reports are both added as visible text attributes rather
  than applied silently, so an analyst can tell a shortened list from a complete one.
• Only the queried indicator leaves the MISP instance. Requests carry a
  scanmalware-misp/1.0 User-Agent.

Measured output

domain  hkr.se            ->  70 attributes  (domain 70)
domain  cloudflare.com    -> 201 attributes  (domain 200 + the cap notice)
url     https://wpsec.com/->  82 attributes  (verdict text, report link, 80 contacted IPs)
ip-src  172.67.216.2      ->   3 attributes  (archive summary + resolved hosts)

Tests

tests/test_scanmalware.py, 12 tests, no network access. They cover the cases that would
otherwise degrade quietly: wildcard certificate entries (*.example.com) being dropped
rather than emitted as hosts, truncation and the result cap both being reported, a URL
being reduced to its host before lookup, an unreachable API degrading instead of raising,
and no auth header ever being sent.

Clean under the repository's own black (line length 120, preview,
string_processing), isort and flake8 settings.

Note on documentation: I deliberately have not committed regenerated
documentation/ output. Running documentation/generate.py locally drops every module
whose optional dependencies are missing, which produced a 4,600-line deletion across
unrelated modules. Happy to add the generated entries if you would like them in this PR,
but it seemed safer to leave that to a run with the full dependency set. The logo is
included since moduleinfo references it.

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Disclosure: I run ScanMalware, so this is a vendor-submitted module. Flagging it up
front rather than leaving it to be found in review.