add format_title helper for notification titles

surfsense_backend/app/notifications/service/messages/text.py

@@ -2,7 +2,21 @@
 
 from __future__ import annotations
 
+from app.notifications.constants import TITLE_MAX_LENGTH
+
 
 def truncate(text: str, limit: int) -> str:
     """Return ``text`` capped at ``limit`` chars, appending an ellipsis if cut."""
     return text[:limit] + "..." if len(text) > limit else text
+
+
+def format_title(prefix: str, text: str, *, max_length: int = TITLE_MAX_LENGTH) -> str:
+    """Build a notification title that fits ``max_length`` including ``prefix``."""
+    budget = max_length - len(prefix)
+    if budget <= 0:
+        return prefix[:max_length]
+    if len(text) <= budget:
+        return f"{prefix}{text}"
+    if budget <= 3:
+        return f"{prefix}{text[:budget]}"
+    return f"{prefix}{text[: budget - 3]}..."