refactor: remove hardcoded credentials from config

- Strip configuration.local.php to logger-only defaults
- Remove db, solr, session, checkfile_url, worker IDs (unused legacy)
- Clean credential comments from logger config files
- Add .env.example template
- Add .env to .gitignore

.env.example

@@ -0,0 +1,6 @@
+# php-bsrutils environment variables
+# This library only needs logging configuration if you override the defaults.
+# Most applications define their own logging config, making this optional.
+
+# Optional: Override default log file location
+# LOG_FILE=/var/log/app/log.txt