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.go

@@ -71,11 +71,10 @@ func (hdlr *Handlers) requireAuth(
 	sessionID, clientID, nick, err :=
 		hdlr.authSession(request)
 	if err != nil {
-		hdlr.respondError(
-			writer, request,
-			"unauthorized",
-			http.StatusUnauthorized,
-		)
+		hdlr.respondJSON(writer, request, map[string]any{
+			"error":   "not registered",
+			"numeric": irc.ErrNotRegistered,
+		}, http.StatusUnauthorized)
 
 		return 0, 0, "", false
 	}
@@ -925,8 +924,8 @@ func (hdlr *Handlers) handlePrivmsg(
 	if target == "" {
 		hdlr.enqueueNumeric(
 			request.Context(), clientID,
-			irc.ErrNeedMoreParams, nick, []string{command},
-			"Not enough parameters",
+			irc.ErrNoRecipient, nick, []string{command},
+			"No recipient given",
 		)
 		hdlr.broker.Notify(sessionID)
 		hdlr.respondJSON(writer, request,
@@ -940,8 +939,8 @@ func (hdlr *Handlers) handlePrivmsg(
 	if len(lines) == 0 {
 		hdlr.enqueueNumeric(
 			request.Context(), clientID,
-			irc.ErrNeedMoreParams, nick, []string{command},
-			"Not enough parameters",
+			irc.ErrNoTextToSend, nick, []string{command},
+			"No text to send",
 		)
 		hdlr.broker.Notify(sessionID)
 		hdlr.respondJSON(writer, request,
@@ -1028,8 +1027,8 @@ func (hdlr *Handlers) handleChannelMsg(
 	if !isMember {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			irc.ErrNotOnChannel, nick, []string{target},
-			"You're not on that channel",
+			irc.ErrCannotSendToChan, nick, []string{target},
+			"Cannot send to channel",
 		)
 
 		return