fix: tolerate invalid member dates in views

src/ccma/domain/dates.py

@@ -79,9 +79,13 @@ def normalize_date_input(value: str, field_name: str) -> str:
 
 
 def format_date_for_display(value: str) -> str:
-    if not value.strip():
+    text = value.strip()
+    if not text:
         return ""
-    parsed = parse_iso_date(value, "Datum")
+    try:
+        parsed = parse_iso_date(text, "Datum")
+    except DateValidationError:
+        return text
     return parsed.strftime(system_date_pattern()) if parsed else ""