feat: implement IRC numerics batch 2 — connection registration, channel ops, user queries

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/db/queries.go

@@ -953,3 +953,125 @@ 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
+}