Refactor parseDaysOfWeek in CronExpressionFormatter (#510)

Refactored the deeply nested `parseDaysOfWeek` function using guard clauses to flatten the logic structure. By returning early on invalid conditions (`dowPart == "*" || domPart != "*" || monthPart != "*"` and `hoursList.size != 1 || minutesList.size != 1`), the remaining function body's indentation is reduced by two levels.

This improves overall code readability and maintainability without altering existing functionality. The change was verified against existing unit tests, which all pass.

app/src/main/java/com/m57/hermescontrol/util/CronExpressionFormatter.kt

@@ -115,9 +115,11 @@ object CronExpressionFormatter {
         hoursList: List<Int>,
         minutesList: List<Int>,
     ): String? {
-        if (dowPart != "*" && domPart == "*" && monthPart == "*") {
+        if (dowPart == "*" || domPart != "*" || monthPart != "*") return null
-            if (hoursList.size == 1 && minutesList.size == 1) {
+        if (hoursList.size != 1 || minutesList.size != 1) return null
+
         val timeStr = formatTime(hoursList[0], minutesList[0])
+
         if (dowPart.contains("-")) {
             val bounds = dowPart.split("-")
             if (bounds.size == 2) {
@@ -130,13 +132,13 @@ object CronExpressionFormatter {
                 }
             }
         }
+
         val dows = parseField(dowPart, 0, 7)
         if (dows.size == 1) {
             val dowName = dowNames[dows[0]]
             return "Every $dowName at $timeStr"
         }
-            }
+
-        }
         return null
     }