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>

internal/db/queries.go

@@ -7,8 +7,10 @@ import (
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"strconv"
 	"time"
 
+	"git.eeqj.de/sneak/neoirc/internal/irc"
 	"github.com/google/uuid"
 )
 
@@ -33,6 +35,7 @@ func generateToken() (string, error) {
 type IRCMessage struct {
 	ID      string          `json:"id"`
 	Command string          `json:"command"`
+	Code    int             `json:"code,omitempty"`
 	From    string          `json:"from,omitempty"`
 	To      string          `json:"to,omitempty"`
 	Params  json.RawMessage `json:"params,omitempty"`
@@ -42,6 +45,15 @@ type IRCMessage struct {
 	DBID    int64           `json:"-"`
 }
 
+// isNumericCode returns true if s is exactly a 3-digit
+// IRC numeric reply code.
+func isNumericCode(s string) bool {
+	return len(s) == 3 &&
+		s[0] >= '0' && s[0] <= '9' &&
+		s[1] >= '0' && s[1] <= '9' &&
+		s[2] >= '0' && s[2] <= '9'
+}
+
 // ChannelInfo is a lightweight channel representation.
 type ChannelInfo struct {
 	ID    int64  `json:"id"`
@@ -717,6 +729,15 @@ func scanMessages(
 		msg.DBID = qID
 		lastQID = qID
 
+		if isNumericCode(msg.Command) {
+			code, _ := strconv.Atoi(msg.Command)
+			msg.Code = code
+
+			if name := irc.Name(code); name != "" {
+				msg.Command = name
+			}
+		}
+
 		msgs = append(msgs, msg)
 	}
 
@@ -953,3 +974,125 @@ func (database *Database) GetSessionChannels(
 
 	return scanChannels(rows)
 }
+
+// GetChannelCount returns the total number of channels.
+func (database *Database) GetChannelCount(
+	ctx context.Context,
+) (int64, error) {
+	var count int64
+
+	err := database.conn.QueryRowContext(
+		ctx,
+		"SELECT COUNT(*) FROM channels",
+	).Scan(&count)
+	if err != nil {
+		return 0, fmt.Errorf(
+			"get channel count: %w", err,
+		)
+	}
+
+	return count, nil
+}
+
+// ChannelInfoFull contains extended channel information.
+type ChannelInfoFull struct {
+	ID          int64  `json:"id"`
+	Name        string `json:"name"`
+	Topic       string `json:"topic"`
+	MemberCount int64  `json:"memberCount"`
+}
+
+// ListAllChannelsWithCounts returns every channel
+// with its member count.
+func (database *Database) ListAllChannelsWithCounts(
+	ctx context.Context,
+) ([]ChannelInfoFull, error) {
+	rows, err := database.conn.QueryContext(ctx,
+		`SELECT c.id, c.name, c.topic,
+		   COUNT(cm.session_id) AS member_count
+		 FROM channels c
+		 LEFT JOIN channel_members cm
+		   ON cm.channel_id = c.id
+		 GROUP BY c.id
+		 ORDER BY c.name`)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"list channels with counts: %w", err,
+		)
+	}
+
+	defer func() { _ = rows.Close() }()
+
+	var out []ChannelInfoFull
+
+	for rows.Next() {
+		var chanInfo ChannelInfoFull
+
+		err = rows.Scan(
+			&chanInfo.ID, &chanInfo.Name,
+			&chanInfo.Topic, &chanInfo.MemberCount,
+		)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"scan channel full: %w", err,
+			)
+		}
+
+		out = append(out, chanInfo)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, fmt.Errorf("rows error: %w", err)
+	}
+
+	if out == nil {
+		out = []ChannelInfoFull{}
+	}
+
+	return out, nil
+}
+
+// GetChannelCreatedAt returns the creation time of a
+// channel.
+func (database *Database) GetChannelCreatedAt(
+	ctx context.Context,
+	channelID int64,
+) (time.Time, error) {
+	var createdAt time.Time
+
+	err := database.conn.QueryRowContext(
+		ctx,
+		"SELECT created_at FROM channels WHERE id = ?",
+		channelID,
+	).Scan(&createdAt)
+	if err != nil {
+		return time.Time{}, fmt.Errorf(
+			"get channel created_at: %w", err,
+		)
+	}
+
+	return createdAt, nil
+}
+
+// GetSessionCreatedAt returns the creation time of a
+// session.
+func (database *Database) GetSessionCreatedAt(
+	ctx context.Context,
+	sessionID int64,
+) (time.Time, error) {
+	var createdAt time.Time
+
+	err := database.conn.QueryRowContext(
+		ctx,
+		"SELECT created_at FROM sessions WHERE id = ?",
+		sessionID,
+	).Scan(&createdAt)
+	if err != nil {
+		return time.Time{}, fmt.Errorf(
+			"get session created_at: %w", err,
+		)
+	}
+
+	return createdAt, nil
+}