Secrets masker: non-string values are not redacted when the key name is sensitive

### Under which category would you file this issue? Airflow Core ### Apache Airflow version 3.3.0 ### What happened and how to reproduce it? **Issue 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. `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: ```python # airflow/_shared/secrets_masker/secrets_masker.py:323-347 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 ``` It is reached from `_redact` line 358: ```python if name and self.should_hide_value_for_key(name): return self._redact_all(item, depth, max_depth, replacement=replacement) ``` 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. **Steps to reproduce** 1. Create Variables whose names contain a sensitive keyword: ```bash airflow variables set test-password-a "abcd" airflow variables set test-password-b "1234" airflow variables set test-password-c "12ab" airflow variables set test-password-d "1234.5" airflow variables set test-password-e "true" ``` 2. Read them back via the API (or view Admin -> Variables in the UI): ```bash curl -H "Authorization: Bearer $TOKEN" \ "http://<airflow>/api/v2/variables?limit=100" ``` 3. Observed: | value | returned | |----------|-----------| | `abcd` | `***` | | `12ab` | `***` | | `1234` | `1234` | | `1234.5` | `1234.5` | | `true` | `true` | Values that are vali…