fix: redact non-string scalar values when key name is sensitive (#71275)

[waterWang]

Description

When a Variable's key name matches the sensitive-keyword list, GET /api/v2/variables correctly returns *** for string values but returns non-string values (int, float, bool) in cleartext, leaking sensitive data.

Root cause

SecretsMasker._redact_all is the fail-closed path used when a key name is judged sensitive, but it only replaces str, recurses into containers, and returns every other type unchanged:

def _redact_all(self, item, depth, max_depth=MAX_RECURSION_DEPTH, *, replacement="***"):
    if depth > max_depth or isinstance(item, str):
        return replacement
    if isinstance(item, dict): ...
    if isinstance(item, (tuple, set)): ...
    if isinstance(item, list): ...
    return item          # <-- non-str scalars pass through unredacted

The comment at lines 353-355 states that key-name-based redaction "must fail closed at any nesting level". It fails closed on depth, but not on type.

Fix

Change the final fall-through in _redact_all from return item to return replacement, so any non-container, non-str scalar (int, float, bool) is also redacted when the key name is sensitive.

Closes #71275