fix: obfuscate additional server secrets values (#9014)
### What problem does this PR solve?
Obfuscates additional secrets values on ragflow_server startup to
prevent leakage:
* `secret` (azure)
* `client_secret` (oauth)
* `http_secret_key` (authentication)
* `sas_token` (azure)
### Type of change
- [x] Bug Fix (non-breaking change which fixes an issue)
Co-authored-by: Gifford R Nowland <gifford.r.nowland@aero.org>