feat: implement IRC numerics batch 2 — connection registration, channel ops, user queries (#59)

## Summary

Implements the remaining important/commonly-used IRC numeric reply codes, as requested in [issue #52](#52).

### Connection Registration (001-005)
- **002 RPL_YOURHOST** — "Your host is <server>, running version <ver>"
- **003 RPL_CREATED** — "This server was created <date>"
- **004 RPL_MYINFO** — "<server> <version> <usermodes> <chanmodes>"
- **005 RPL_ISUPPORT** — CHANTYPES=#, NICKLEN=32, CHANMODES, NETWORK=neoirc, CASEMAPPING=ascii

All sent automatically after RPL_WELCOME during session creation/login.

### Server Statistics (251-255)
- **251 RPL_LUSERCLIENT** — user count
- **252 RPL_LUSEROP** — operator count
- **254 RPL_LUSERCHANNELS** — channel count
- **255 RPL_LUSERME** — local client count

Sent during connection registration and available via LUSERS command.

### Channel Operations
- **MODE command** — query channel modes (324 RPL_CHANNELMODEIS + 329 RPL_CREATIONTIME) and user modes (221 RPL_UMODEIS)
- **NAMES command** — query channel member list (reuses 353/366)
- **LIST command** — list all channels with member counts (322 RPL_LIST + 323 end)

### User Queries
- **WHOIS command** — 311 RPL_WHOISUSER, 312 RPL_WHOISSERVER, 319 RPL_WHOISCHANNELS, 318 RPL_ENDOFWHOIS
- **WHO command** — 352 RPL_WHOREPLY, 315 RPL_ENDOFWHO

### Database Additions
- `GetChannelCount()` — total channel count for LUSERS
- `ListAllChannelsWithCounts()` — channels with member counts for LIST
- `GetChannelCreatedAt()` — channel creation time for RPL_CREATIONTIME
- `GetSessionCreatedAt()` — session creation time

### Other Changes
- Added `StartTime` to `Globals` struct for RPL_CREATED
- Updated README with comprehensive documentation of all new commands and numerics
- Updated roadmap to reflect implemented features

`docker build .` passes (lint, tests, build all green).

closes [#52](#52)

<!-- session: agent:sdlc-manager:subagent:1f3dcab8-ad6a-4c4c-af72-34a617640c9d -->

Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: clawbot <clawbot@git.eeqj.de>
Reviewed-on: #59
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>
Co-committed-by: clawbot <sneak+clawbot@sneak.cloud>

cmd/neoirc-cli/api/client.go

@@ -13,6 +13,8 @@ import (
 	"strconv"
 	"strings"
 	"time"
+
+	"git.eeqj.de/sneak/neoirc/internal/irc"
 )
 
 const (
@@ -168,7 +170,7 @@ func (client *Client) PollMessages(
 func (client *Client) JoinChannel(channel string) error {
 	return client.SendMessage(
 		&Message{ //nolint:exhaustruct // only command+to needed
-			Command: "JOIN", To: channel,
+			Command: irc.CmdJoin, To: channel,
 		},
 	)
 }
@@ -177,7 +179,7 @@ func (client *Client) JoinChannel(channel string) error {
 func (client *Client) PartChannel(channel string) error {
 	return client.SendMessage(
 		&Message{ //nolint:exhaustruct // only command+to needed
-			Command: "PART", To: channel,
+			Command: irc.CmdPart, To: channel,
 		},
 	)
 }

cmd/neoirc-cli/main.go

@@ -9,6 +9,7 @@ import (
 	"time"
 
 	api "git.eeqj.de/sneak/neoirc/cmd/neoirc-cli/api"
+	"git.eeqj.de/sneak/neoirc/internal/irc"
 )
 
 const (
@@ -86,7 +87,7 @@ func (a *App) handleInput(text string) {
 	}
 
 	err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-		Command: "PRIVMSG",
+		Command: irc.CmdPrivmsg,
 		To:      target,
 		Body:    []string{text},
 	})
@@ -241,7 +242,7 @@ func (a *App) cmdNick(nick string) {
 	}
 
 	err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-		Command: "NICK",
+		Command: irc.CmdNick,
 		Body:    []string{nick},
 	})
 	if err != nil {
@@ -376,7 +377,7 @@ func (a *App) cmdMsg(args string) {
 	}
 
 	err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-		Command: "PRIVMSG",
+		Command: irc.CmdPrivmsg,
 		To:      target,
 		Body:    []string{text},
 	})
@@ -434,7 +435,7 @@ func (a *App) cmdTopic(args string) {
 
 	if args == "" {
 		err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-			Command: "TOPIC",
+			Command: irc.CmdTopic,
 			To:      target,
 		})
 		if err != nil {
@@ -447,7 +448,7 @@ func (a *App) cmdTopic(args string) {
 	}
 
 	err := a.client.SendMessage(&api.Message{ //nolint:exhaustruct
-		Command: "TOPIC",
+		Command: irc.CmdTopic,
 		To:      target,
 		Body:    []string{args},
 	})
@@ -535,7 +536,7 @@ func (a *App) cmdMotd() {
 	}
 
 	err := a.client.SendMessage(
-		&api.Message{Command: "MOTD"}, //nolint:exhaustruct
+		&api.Message{Command: irc.CmdMotd}, //nolint:exhaustruct
 	)
 	if err != nil {
 		a.ui.AddStatus(fmt.Sprintf(
@@ -572,7 +573,7 @@ func (a *App) cmdWho(args string) {
 
 	err := a.client.SendMessage(
 		&api.Message{ //nolint:exhaustruct
-			Command: "WHO", To: channel,
+			Command: irc.CmdWho, To: channel,
 		},
 	)
 	if err != nil {
@@ -603,7 +604,7 @@ func (a *App) cmdWhois(args string) {
 
 	err := a.client.SendMessage(
 		&api.Message{ //nolint:exhaustruct
-			Command: "WHOIS", To: args,
+			Command: irc.CmdWhois, To: args,
 		},
 	)
 	if err != nil {
@@ -653,7 +654,7 @@ func (a *App) cmdQuit() {
 
 	if a.connected && a.client != nil {
 		_ = a.client.SendMessage(
-			&api.Message{Command: "QUIT"}, //nolint:exhaustruct
+			&api.Message{Command: irc.CmdQuit}, //nolint:exhaustruct
 		)
 	}
 
@@ -738,19 +739,19 @@ func (a *App) handleServerMessage(msg *api.Message) {
 	a.mu.Unlock()
 
 	switch msg.Command {
-	case "PRIVMSG":
+	case irc.CmdPrivmsg:
 		a.handlePrivmsgEvent(msg, timestamp, myNick)
-	case "JOIN":
+	case irc.CmdJoin:
 		a.handleJoinEvent(msg, timestamp)
-	case "PART":
+	case irc.CmdPart:
 		a.handlePartEvent(msg, timestamp)
-	case "QUIT":
+	case irc.CmdQuit:
 		a.handleQuitEvent(msg, timestamp)
-	case "NICK":
+	case irc.CmdNick:
 		a.handleNickEvent(msg, timestamp, myNick)
-	case "NOTICE":
+	case irc.CmdNotice:
 		a.handleNoticeEvent(msg, timestamp)
-	case "TOPIC":
+	case irc.CmdTopic:
 		a.handleTopicEvent(msg, timestamp)
 	default:
 		a.handleDefaultEvent(msg, timestamp)