maven: calendar event querying (task 3)

Store: CalendarEvents(ctx, from, to) — filters caldav facts by key date prefix.
IPC: full wiring through interface, server dispatch, and client.
Router: ParseCalendarDate (сегодня/завтра), CalendarEventFormatter (RU reply).
Voice: calendar detection before notes RAG in IntentQuery handler.
Tests: store integration test, date parser tests, formatter tests.

Co-Authored-By: opencode <opencode@anthropic.com>

internal/router/slots.go

@@ -327,3 +327,17 @@ func parseDurationValue(s string) (string, bool) {
 	}
 	return strconv.Itoa(n) + unit, true
 }
+
+// ParseCalendarDate detects RU calendar date words in text and returns the
+// resolved time (midnight UTC+0 for "сегодня"/"today", next day for "завтра"/"tomorrow").
+// Returns zero time + false if no match.
+func ParseCalendarDate(text string, now time.Time) (time.Time, bool) {
+	lower := strings.ToLower(text)
+	if strings.Contains(lower, "сегодня") || strings.Contains(lower, "today") {
+		return now.Truncate(24 * time.Hour), true
+	}
+	if strings.Contains(lower, "завтра") || strings.Contains(lower, "tomorrow") {
+		return now.Truncate(24 * time.Hour).Add(24 * time.Hour), true
+	}
+	return time.Time{}, false
+}