fix: extract repeated IRC command string literals to constants (goconst)

Add comprehensive IRC numeric reply support:

Connection registration (001-005):
- 002 RPL_YOURHOST, 003 RPL_CREATED, 004 RPL_MYINFO, 005 RPL_ISUPPORT
- All sent automatically during session creation after RPL_WELCOME

Server statistics (251-255):
- RPL_LUSERCLIENT, RPL_LUSEROP, RPL_LUSERCHANNELS, RPL_LUSERME
- Sent during connection registration and via LUSERS command

Channel operations:
- MODE command: query channel modes (324 RPL_CHANNELMODEIS, 329 RPL_CREATIONTIME)
- MODE command: query user modes (221 RPL_UMODEIS)
- NAMES command: query channel member list (353/366)
- LIST command: list all channels (322 RPL_LIST, 323 end of list)

User queries:
- WHOIS command: 311/312/318/319 numerics
- WHO command: 352 RPL_WHOREPLY, 315 RPL_ENDOFWHO

Database additions:
- GetChannelCount, ListAllChannelsWithCounts
- GetChannelCreatedAt, GetSessionCreatedAt

Also adds StartTime to Globals for RPL_CREATED and updates README
with comprehensive documentation of all new commands and numerics.

closes #52

internal/handlers/api.go

@@ -27,7 +27,15 @@ const (
 	defaultMaxBodySize = 4096
 	defaultHistLimit   = 50
 	maxHistLimit       = 500
+	cmdJoin            = "JOIN"
+	cmdList            = "LIST"
+	cmdNick            = "NICK"
+	cmdPart            = "PART"
 	cmdPrivmsg         = "PRIVMSG"
+	cmdQuit            = "QUIT"
+	cmdTopic           = "TOPIC"
+	cmdWho             = "WHO"
+	cmdWhois           = "WHOIS"
 )
 
 func (hdlr *Handlers) maxBodySize() int64 {
@@ -756,32 +764,32 @@ func (hdlr *Handlers) dispatchCommand(
 			sessionID, clientID, nick,
 			command, target, body, bodyLines,
 		)
-	case "JOIN":
+	case cmdJoin:
 		hdlr.handleJoin(
 			writer, request,
 			sessionID, clientID, nick, target,
 		)
-	case "PART":
+	case cmdPart:
 		hdlr.handlePart(
 			writer, request,
 			sessionID, clientID, nick, target, body,
 		)
-	case "NICK":
+	case cmdNick:
 		hdlr.handleNick(
 			writer, request,
 			sessionID, clientID, nick, bodyLines,
 		)
-	case "TOPIC":
+	case cmdTopic:
 		hdlr.handleTopic(
 			writer, request,
 			sessionID, clientID, nick,
 			target, body, bodyLines,
 		)
-	case "QUIT":
+	case cmdQuit:
 		hdlr.handleQuit(
 			writer, request, sessionID, nick, body,
 		)
-	case "MOTD", "LIST", "WHO", "WHOIS", "PING":
+	case "MOTD", cmdList, cmdWho, cmdWhois, "PING":
 		hdlr.dispatchInfoCommand(
 			writer, request,
 			sessionID, clientID, nick,
@@ -815,18 +823,18 @@ func (hdlr *Handlers) dispatchQueryCommand(
 			writer, request,
 			sessionID, clientID, nick, target,
 		)
-	case "LIST":
+	case cmdList:
 		hdlr.handleList(
 			writer, request,
 			sessionID, clientID, nick,
 		)
-	case "WHOIS":
+	case cmdWhois:
 		hdlr.handleWhois(
 			writer, request,
 			sessionID, clientID, nick,
 			target, bodyLines,
 		)
-	case "WHO":
+	case cmdWho:
 		hdlr.handleWho(
 			writer, request,
 			sessionID, clientID, nick, target,
@@ -1073,7 +1081,7 @@ func (hdlr *Handlers) handleJoin(
 	if target == "" {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"JOIN"},
+			"461", nick, []string{cmdJoin},
 			"Not enough parameters",
 		)
 
@@ -1144,7 +1152,7 @@ func (hdlr *Handlers) executeJoin(
 	)
 
 	_ = hdlr.fanOutSilent(
-		request, "JOIN", nick, channel, nil, memberIDs,
+		request, cmdJoin, nick, channel, nil, memberIDs,
 	)
 
 	hdlr.deliverJoinNumerics(
@@ -1242,7 +1250,7 @@ func (hdlr *Handlers) handlePart(
 	if target == "" {
 		hdlr.enqueueNumeric(
 			request.Context(), clientID,
-			"461", nick, []string{"PART"},
+			"461", nick, []string{cmdPart},
 			"Not enough parameters",
 		)
 		hdlr.broker.Notify(sessionID)
@@ -1280,7 +1288,7 @@ func (hdlr *Handlers) handlePart(
 	)
 
 	_ = hdlr.fanOutSilent(
-		request, "PART", nick, channel, body, memberIDs,
+		request, cmdPart, nick, channel, body, memberIDs,
 	)
 
 	err = hdlr.params.Database.PartChannel(
@@ -1322,7 +1330,7 @@ func (hdlr *Handlers) handleNick(
 	if len(lines) == 0 {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"NICK"},
+			"461", nick, []string{cmdNick},
 			"Not enough parameters",
 		)
 
@@ -1420,7 +1428,7 @@ func (hdlr *Handlers) broadcastNick(
 	}
 
 	dbID, _, _ := hdlr.params.Database.InsertMessage(
-		request.Context(), "NICK", oldNick, "",
+		request.Context(), cmdNick, oldNick, "",
 		nil, json.RawMessage(nickBody), nil,
 	)
 
@@ -1461,7 +1469,7 @@ func (hdlr *Handlers) handleTopic(
 	if target == "" {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"TOPIC"},
+			"461", nick, []string{cmdTopic},
 			"Not enough parameters",
 		)
 
@@ -1472,7 +1480,7 @@ func (hdlr *Handlers) handleTopic(
 	if len(lines) == 0 {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"TOPIC"},
+			"461", nick, []string{cmdTopic},
 			"Not enough parameters",
 		)
 
@@ -1534,7 +1542,7 @@ func (hdlr *Handlers) executeTopic(
 	)
 
 	_ = hdlr.fanOutSilent(
-		request, "TOPIC", nick, channel, body, memberIDs,
+		request, cmdTopic, nick, channel, body, memberIDs,
 	)
 
 	hdlr.enqueueNumeric(
@@ -1567,16 +1575,16 @@ func (hdlr *Handlers) dispatchInfoCommand(
 		hdlr.deliverMOTD(
 			request, clientID, sessionID, nick,
 		)
-	case "LIST":
+	case cmdList:
 		hdlr.handleListCmd(
 			request, clientID, sessionID, nick,
 		)
-	case "WHO":
+	case cmdWho:
 		hdlr.handleWhoCmd(
 			request, clientID, sessionID, nick,
 			target,
 		)
-	case "WHOIS":
+	case cmdWhois:
 		hdlr.handleWhoisCmd(
 			request, clientID, sessionID, nick,
 			target, bodyLines,
@@ -1657,7 +1665,7 @@ func (hdlr *Handlers) handleWhoCmd(
 	if target == "" {
 		hdlr.enqueueNumeric(
 			ctx, clientID, "461", nick,
-			[]string{"WHO"}, "Not enough parameters",
+			[]string{cmdWho}, "Not enough parameters",
 		)
 		hdlr.broker.Notify(sessionID)
 
@@ -1728,7 +1736,7 @@ func (hdlr *Handlers) handleWhoisCmd(
 	if whoisNick == "" {
 		hdlr.enqueueNumeric(
 			ctx, clientID, "461", nick,
-			[]string{"WHOIS"}, "Not enough parameters",
+			[]string{cmdWhois}, "Not enough parameters",
 		)
 		hdlr.broker.Notify(sessionID)
 
@@ -1831,7 +1839,7 @@ func (hdlr *Handlers) handleQuit(
 
 	if len(channels) > 0 {
 		dbID, _, _ = hdlr.params.Database.InsertMessage(
-			request.Context(), "QUIT", nick, "",
+			request.Context(), cmdQuit, nick, "",
 			nil, body, nil,
 		)
 	}
@@ -2100,7 +2108,7 @@ func (hdlr *Handlers) handleWhois(
 	if queryNick == "" {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"WHOIS"},
+			"461", nick, []string{cmdWhois},
 			"Not enough parameters",
 		)
 
@@ -2211,7 +2219,7 @@ func (hdlr *Handlers) handleWho(
 	if target == "" {
 		hdlr.respondIRCError(
 			writer, request, clientID, sessionID,
-			"461", nick, []string{"WHO"},
+			"461", nick, []string{cmdWho},
 			"Not enough parameters",
 		)
 
@@ -2499,7 +2507,7 @@ func (hdlr *Handlers) cleanupUser(
 
 	if len(channels) > 0 {
 		quitDBID, _, _ = hdlr.params.Database.InsertMessage(
-			ctx, "QUIT", nick, "",
+			ctx, cmdQuit, nick, "",
 			nil, nil, nil,
 		)
 	}