reminders: confirm from the row, not from the sentence (V-507)

The confirmation was phrased by the replier off Slots.Text, so it named
whatever hour the utterance contained — including one the parser rejected
or read differently. He heard 'напомню в семь' with no row at seven, and
stopped thinking about it.

actionReminder now phrases it itself from the stored fire time, so the
sentence and the row cannot disagree. Deterministic: the one sentence that
must match a database row is not one to hand to a 1.7B.

Also fixes formatTime, which had t.Format("2 января") — Go reads that as a
literal, so every fact older than a day read as January. The month comes
from internal/lexicon now, which is where months live.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

cmd/mavend/ruwords.go

@@ -165,6 +165,8 @@ func formatTime(t time.Time) string {
 		n := int(diff.Hours())
 		return fmt.Sprintf("%d %s назад", n, say.CountWord(n, "час", "часа", "часов"))
 	default:
-		return t.Format("2 января 15:04")
+		// Not t.Format("2 января …"): Go reads that as a literal, so every
+		// fact older than a day used to read as January (Vikunja #507).
+		return fmt.Sprintf("%d %s %s", t.Day(), lexicon.MonthGenitive(int(t.Month())), t.Format("15:04"))
 	}
 }