fix: resolve go vet error and dayStart logic in ComputeDailyTotals

- Fix 'string(d)' int-to-rune conversion in rpg_test.go by using fmt.Sprintf
- Fix ComputeDailyTotals dayStart logic: initial state should be StateWorking
  when dayStart > 0, correctly counting work from dayStart to first out event
- Update README project structure to reflect new domain/handler/repo layout
- Implement missing achievements: rpg_pioneer (on RPG enable) and
  salary_setter (on first rate set)
- Add tryUnlockAchievement helper to Handler

internal/domain/totals.go

@@ -0,0 +1,68 @@
+package domain
+
+import "sort"
+
+// ComputeDailyTotals calculates the total work and break time from a list of events.
+func ComputeDailyTotals(events []Event, minBreakThreshold int64, dayStart, dayEnd int64) DailyTotals {
+	if len(events) == 0 {
+		return DailyTotals{}
+	}
+
+	sorted := make([]Event, len(events))
+	copy(sorted, events)
+	sort.Slice(sorted, func(i, j int) bool {
+		return sorted[i].OccurredAt < sorted[j].OccurredAt
+	})
+
+	var totalWork, totalBreak int64
+	state := StateIdle
+	var workStart, breakStart int64
+
+	if dayStart > 0 {
+		state = StateWorking
+		workStart = dayStart
+	} else if sorted[0].EventType == "out" {
+		state = StateOnBreak
+	}
+
+	for _, e := range sorted {
+		switch {
+		case e.EventType == "in" && state == StateIdle:
+			state = StateWorking
+			workStart = e.OccurredAt
+		case e.EventType == "in" && state == StateOnBreak:
+			breakElapsed := e.OccurredAt - breakStart
+			if breakElapsed >= minBreakThreshold {
+				totalBreak += breakElapsed
+			} else {
+				totalWork += breakElapsed
+			}
+			state = StateWorking
+			workStart = e.OccurredAt
+		case e.EventType == "in" && state == StateWorking:
+		case e.EventType == "out" && state == StateWorking:
+			totalWork += e.OccurredAt - workStart
+			state = StateOnBreak
+			breakStart = e.OccurredAt
+		case e.EventType == "out" && state == StateOnBreak:
+			breakStart = e.OccurredAt
+		case e.EventType == "out" && state == StateIdle:
+			state = StateOnBreak
+			breakStart = e.OccurredAt
+		}
+	}
+
+	if state == StateWorking && dayEnd > 0 {
+		totalWork += dayEnd - workStart
+	}
+	if state == StateOnBreak && dayEnd > 0 {
+		breakElapsed := dayEnd - breakStart
+		if breakElapsed >= minBreakThreshold {
+			totalBreak += breakElapsed
+		} else {
+			totalWork += breakElapsed
+		}
+	}
+
+	return DailyTotals{TotalSeconds: totalWork, BreakSeconds: totalBreak}
+}