Fix bash conditional expression syntax error in date range loop

Split compound conditional into separate [[ ]] tests to resolve
syntax error on line 184 when using date range filtering.

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

legacy/exitrace/exitrace.sh

@@ -181,7 +181,7 @@ determine_logfiles() {
     local current_date="$start_date"
     # Hinweis: In [[ ]] gibt es kein '<=' String-Operator.
     # Daher explizit 'kleiner als ODER gleich' prüfen.
-    while [[ "$current_date" < "$end_date" || "$current_date" == "$end_date" ]]; do
+    while [[ "$current_date" < "$end_date" ]] || [[ "$current_date" == "$end_date" ]]; do
       local year month
       year=$(date -d "$current_date" +%Y)
       month=$(date -d "$current_date" +%m)