docs(dev): document registerSensitiveMethods() in logging.rst - #15705

Summary

Documents IRegistrationContext::registerSensitiveMethods() in developer_manual/basics/logging.rst so app authors know how to keep secrets out of logged exception stack traces.

• New section after Logging exceptions: register methods that accept secrets during bootstrap; the logger redacts those arguments in stack traces.
• Short code example using Application::register().
• Note that this only covers stack traces — never put passwords, tokens, or personal data into a log message yourself.

Closes #15680

Test plan

• Sphinx build of the developer manual succeeds for the logging page
• Section documents registerSensitiveMethods() with class + method-name array
• Note states redaction is stack-trace-only; secrets must not be logged in messages

AI disclosure

This PR was drafted with the help of AI coding assistants (Cursor agents / LLM-based tools), including the description. I am responsible for it and happy to rework anything that doesn't fit.

All commits carry an Assisted-by: Cursor:grok-4.7 trailer.