Fix string comparison operator in date range loop

Replace <= operator with explicit 'less than OR equal' logic in bash [[ ]] context.

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Co-Authored-By: Claude <noreply@anthropic.com>

legacy/exitrace/exitrace.sh

@@ -179,7 +179,9 @@ determine_logfiles() {
     validate_date "$end_date"
     
     local current_date="$start_date"
-    while [[ "$current_date" <= "$end_date" ]]; do
+    # Hinweis: In [[ ]] gibt es kein '<=' String-Operator.
+    # Daher explizit 'kleiner als ODER gleich' prüfen.
+    while [[ "$current_date" < "$end_date" || "$current_date" == "$end_date" ]]; do
       local year month
       year=$(date -d "$current_date" +%Y)
       month=$(date -d "$current_date" +%m)