Add Holehe collector for email targets

Closes the email target-type gap (previously had zero collectors).
Checks whether an email is registered on 120+ sites via the
password-reset-oracle technique. Shares the Sherlock/whois venv.

HoleheRunner gates success on the CSV file existing rather than the
process exit code: holehe's CLI calls Python's exit("message") right
after writing results on its normal success path, which always yields
exit code 1 regardless of outcome — discovered while verifying this
end-to-end against the real dev server and queue worker.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/python/README.md

@@ -7,8 +7,8 @@ scripts/python/setup.sh
 ```
 
 Sets up:
-- `scripts/python/.venv` — Sherlock (`sherlock-project`) and `python-whois`,
-  both lightweight and dependency-compatible.
+- `scripts/python/.venv` — Sherlock (`sherlock-project`), `python-whois`,
+  and Holehe, all lightweight and dependency-compatible.
 - `scripts/python/.venv-theharvester` — theHarvester, isolated because it
   pulls in a much heavier dependency set (playwright, censys, shodan,
   fastapi). Vendored from `theharvester-src/` at tag `4.6.0` (the last