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/reactive_notes_test.go

@@ -44,9 +44,12 @@ func TestReactiveNotesReminders(t *testing.T) {
 				HasTime: true,
 			},
 		}
+		// The confirmation is phrased from the row now (Vikunja #507), so it
+		// names the stored hour rather than leaving the replier to read one
+		// out of the sentence.
 		reply := h.applyAction(ctx, dec)
-		if reply != "" {
-			t.Errorf("expected empty reply from applyAction, got %q", reply)
+		if want := "хорошо, напомню завтра в " + fireAt.Format("15:04") + "."; reply != want {
+			t.Errorf("reply = %q, want %q", reply, want)
 		}
 		reminders, err := st.ListReminders(ctx, 10)
 		if err != nil {