feat: implement Tier 3 utility IRC commands

Implement all 7 utility IRC commands from issue #87:

User commands:
- USERHOST: quick lookup of user@host for up to 5 nicks (RPL 302)
- VERSION: server version string using globals.Version (RPL 351)
- ADMIN: server admin contact info (RPL 256-259)
- INFO: server software info text (RPL 371/374)
- TIME: server local time in RFC format (RPL 391)

Oper commands:
- KILL: forcibly disconnect a user (requires is_oper), broadcasts
  QUIT to all shared channels, cleans up sessions
- WALLOPS: broadcast message to all users with +w usermode
  (requires is_oper)

Supporting changes:
- Add is_wallops column to sessions table in 001_initial.sql
- Add user mode +w tracking via MODE nick +w/-w
- User mode queries now return actual modes (+o, +w)
- MODE -o allows de-opering yourself; MODE +o rejected
- MODE for other users returns ERR_USERSDONTMATCH (502)
- Extract dispatch helpers to reduce dispatchCommand complexity

Tests cover all commands including error cases, oper checks,
user mode set/unset, KILL broadcast, WALLOPS delivery, and
edge cases (self-kill, nonexistent users, missing params).

closes #87

internal/handlers/api.go

@@ -1014,10 +1014,12 @@ func (hdlr *Handlers) dispatchCommand(
 	bodyLines func() []string,
 ) {
 	switch command {
-	case irc.CmdAway:
-		hdlr.handleAway(
+	case irc.CmdAway, irc.CmdNick,
+		irc.CmdPass, irc.CmdInvite:
+		hdlr.dispatchBodyOnlyCommand(
 			writer, request,
-			sessionID, clientID, nick, bodyLines,
+			sessionID, clientID, nick,
+			command, bodyLines,
 		)
 	case irc.CmdPrivmsg, irc.CmdNotice:
 		hdlr.handlePrivmsg(
@@ -1036,27 +1038,12 @@ func (hdlr *Handlers) dispatchCommand(
 			writer, request,
 			sessionID, clientID, nick, target, body,
 		)
-	case irc.CmdNick:
-		hdlr.handleNick(
-			writer, request,
-			sessionID, clientID, nick, bodyLines,
-		)
-	case irc.CmdPass:
-		hdlr.handlePass(
-			writer, request,
-			sessionID, clientID, nick, bodyLines,
-		)
 	case irc.CmdTopic:
 		hdlr.handleTopic(
 			writer, request,
 			sessionID, clientID, nick,
 			target, body, bodyLines,
 		)
-	case irc.CmdInvite:
-		hdlr.handleInvite(
-			writer, request,
-			sessionID, clientID, nick, bodyLines,
-		)
 	case irc.CmdKick:
 		hdlr.handleKick(
 			writer, request,
@@ -1067,12 +1054,15 @@ func (hdlr *Handlers) dispatchCommand(
 		hdlr.handleQuit(
 			writer, request, sessionID, nick, body,
 		)
-	case irc.CmdOper:
-		hdlr.handleOper(
+	case irc.CmdOper, irc.CmdKill, irc.CmdWallops:
+		hdlr.dispatchOperCommand(
 			writer, request,
-			sessionID, clientID, nick, bodyLines,
+			sessionID, clientID, nick,
+			command, bodyLines,
 		)
-	case irc.CmdMotd, irc.CmdPing:
+	case irc.CmdMotd, irc.CmdPing,
+		irc.CmdVersion, irc.CmdAdmin,
+		irc.CmdInfo, irc.CmdTime:
 		hdlr.dispatchInfoCommand(
 			writer, request,
 			sessionID, clientID, nick,
@@ -1127,6 +1117,11 @@ func (hdlr *Handlers) dispatchQueryCommand(
 			writer, request,
 			sessionID, clientID, nick,
 		)
+	case irc.CmdUserhost:
+		hdlr.handleUserhost(
+			writer, request,
+			sessionID, clientID, nick, bodyLines,
+		)
 	default:
 		hdlr.enqueueNumeric(
 			request.Context(), clientID,
@@ -2416,7 +2411,8 @@ func (hdlr *Handlers) executeTopic(
 }
 
 // dispatchInfoCommand handles informational IRC commands
-// that produce server-side numerics (MOTD, PING).
+// that produce server-side numerics (MOTD, PING,
+// VERSION, ADMIN, INFO, TIME).
 func (hdlr *Handlers) dispatchInfoCommand(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -2442,6 +2438,34 @@ func (hdlr *Handlers) dispatchInfoCommand(
 			},
 			http.StatusOK)
 
+		return
+	case irc.CmdVersion:
+		hdlr.handleVersion(
+			writer, request,
+			sessionID, clientID, nick,
+		)
+
+		return
+	case irc.CmdAdmin:
+		hdlr.handleAdmin(
+			writer, request,
+			sessionID, clientID, nick,
+		)
+
+		return
+	case irc.CmdInfo:
+		hdlr.handleInfo(
+			writer, request,
+			sessionID, clientID, nick,
+		)
+
+		return
+	case irc.CmdTime:
+		hdlr.handleTime(
+			writer, request,
+			sessionID, clientID, nick,
+		)
+
 		return
 	}
 
@@ -2532,15 +2556,11 @@ func (hdlr *Handlers) handleMode(
 
 	channel := target
 	if !strings.HasPrefix(channel, "#") {
-		// User mode query — return empty modes.
-		hdlr.enqueueNumeric(
-			request.Context(), clientID,
-			irc.RplUmodeIs, nick, nil, "+",
+		hdlr.handleUserMode(
+			writer, request,
+			sessionID, clientID, nick, target,
+			bodyLines,
 		)
-		hdlr.broker.Notify(sessionID)
-		hdlr.respondJSON(writer, request,
-			map[string]string{"status": "ok"},
-			http.StatusOK)
 
 		return
 	}