fix: remove dead code, fold migration 002 into 001, implement error numerics

- Remove unused GetAwayByNick() from queries.go
- Delete migration 002; fold away_message and topic_set_by/topic_set_at
  columns into migration 001 (pre-1.0 policy: single migration file)
- PRIVMSG/NOTICE missing target now sends 411 ERR_NORECIPIENT
- PRIVMSG/NOTICE missing body now sends 412 ERR_NOTEXTTOSEND
- Non-member channel send now sends 404 ERR_CANNOTSENDTOCHAN
- Auth failure now returns 451 ERR_NOTREGISTERED numeric in response
- Update test assertions to match correct IRC numerics

internal/handlers/api_test.go

@@ -810,9 +810,9 @@ func TestMessageMissingBody(t *testing.T) {
 
 	msgs, _ := tserver.pollMessages(token, lastID)
 
-	if !findNumeric(msgs, "461") {
+	if !findNumeric(msgs, "412") {
 		t.Fatalf(
-			"expected ERR_NEEDMOREPARAMS (461), got %v",
+			"expected ERR_NOTEXTTOSEND (412), got %v",
 			msgs,
 		)
 	}
@@ -834,9 +834,9 @@ func TestMessageMissingTo(t *testing.T) {
 
 	msgs, _ := tserver.pollMessages(token, lastID)
 
-	if !findNumeric(msgs, "461") {
+	if !findNumeric(msgs, "411") {
 		t.Fatalf(
-			"expected ERR_NEEDMOREPARAMS (461), got %v",
+			"expected ERR_NORECIPIENT (411), got %v",
 			msgs,
 		)
 	}
@@ -869,9 +869,9 @@ func TestNonMemberCannotSend(t *testing.T) {
 
 	msgs, _ := tserver.pollMessages(aliceToken, lastID)
 
-	if !findNumeric(msgs, "442") {
+	if !findNumeric(msgs, "404") {
 		t.Fatalf(
-			"expected ERR_NOTONCHANNEL (442), got %v",
+			"expected ERR_CANNOTSENDTOCHAN (404), got %v",
 			msgs,
 		)
 	}