refactor: separate config service from jail config service

- Split config_service.py into config_service.py and jail_config_service.py
- Update Docs/Tasks.md, Security.md, TROUBLESHOOTING.md

backend/app/services/config_service.py

@@ -98,17 +98,26 @@ async def _safe_get_typed[T](
 
 
 def _validate_regex(pattern: str) -> str | None:
-    """Try to compile *pattern* and return an error message if invalid.
+    """Validate *pattern* for syntax correctness and ReDoS vulnerabilities.
 
     Args:
         pattern: A regex pattern string to validate.
 
     Returns:
-        ``None`` if valid, or an error message string if the pattern is broken.
+        ``None`` if valid, or an error message string if the pattern is broken
+        or detected as a ReDoS vulnerability.
     """
+    from app.utils.regex_validator import (
+        ReDoSDetectedError,
+        RegexTimeoutError,
+        validate_regex_pattern,
+    )
+
     try:
-        re.compile(pattern)
+        validate_regex_pattern(pattern)
         return None
+    except (ReDoSDetectedError, RegexTimeoutError) as exc:
+        return str(exc)
     except re.error as exc:
         return str(exc)