fix: regenerate secrets baseline (#15)

## Summary
- Regenerated `.secrets.baseline` with all 27 detect-secrets plugins
- Previous baseline had empty `plugins_used` and 0 results (corrupt)
- New baseline correctly detects 6 placeholder/template secret keywords
in README.md, config_template.json, and systemd/install.sh

## Test plan
- [x] Verified baseline parses as valid JSON
- [x] Confirmed 27 plugins loaded
- [x] Confirmed 6 detected results are all template placeholders, no
real secrets

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Chores**
* Updated secrets detection baseline configuration from version 1.4.0 to
1.5.0
* Enhanced detector plugins with expanded coverage including entropy,
token, key, and credential detection capabilities
* Improved filtering mechanisms with multiple heuristic filters for
refined detection accuracy
  * Added timestamp tracking for baseline generation

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: bakerboy448