add IP to sessions, IP+hostname to clients

- Add ip column to sessions table (real client IP of session creator)
- Add ip and hostname columns to clients table (per-connection tracking)
- Update CreateSession, RegisterUser, LoginUser to store new fields
- Add GetClientHostInfo query method
- Update SessionHostInfo to include IP
- Extract executeCreateSession to fix funlen lint
- Add tests for session IP, client IP/hostname, login client tracking
- Update README with new field documentation

internal/db/auth.go

@@ -20,7 +20,7 @@ var errNoPassword = errors.New(
 // and returns session ID, client ID, and token.
 func (database *Database) RegisterUser(
 	ctx context.Context,
-	nick, password, username, hostname string,
+	nick, password, username, hostname, remoteIP string,
 ) (int64, int64, string, error) {
 	if username == "" {
 		username = nick
@@ -54,11 +54,11 @@ func (database *Database) RegisterUser(
 
 	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO sessions
-		 (uuid, nick, username, hostname,
+		 (uuid, nick, username, hostname, ip,
 		  password_hash, created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
 		sessionUUID, nick, username, hostname,
-		string(hash), now, now)
+		remoteIP, string(hash), now, now)
 	if err != nil {
 		_ = transaction.Rollback()
 
@@ -73,10 +73,11 @@ func (database *Database) RegisterUser(
 
 	clientRes, err := transaction.ExecContext(ctx,
 		`INSERT INTO clients
-		 (uuid, session_id, token,
+		 (uuid, session_id, token, ip, hostname,
 		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?)`,
-		clientUUID, sessionID, tokenHash, now, now)
+		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
+		clientUUID, sessionID, tokenHash,
+		remoteIP, hostname, now, now)
 	if err != nil {
 		_ = transaction.Rollback()
 
@@ -101,7 +102,7 @@ func (database *Database) RegisterUser(
 // client token.
 func (database *Database) LoginUser(
 	ctx context.Context,
-	nick, password string,
+	nick, password, remoteIP, hostname string,
 ) (int64, int64, string, error) {
 	var (
 		sessionID    int64
@@ -148,10 +149,11 @@ func (database *Database) LoginUser(
 
 	res, err := database.conn.ExecContext(ctx,
 		`INSERT INTO clients
-		 (uuid, session_id, token,
+		 (uuid, session_id, token, ip, hostname,
 		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?)`,
-		clientUUID, sessionID, tokenHash, now, now)
+		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
+		clientUUID, sessionID, tokenHash,
+		remoteIP, hostname, now, now)
 	if err != nil {
 		return 0, 0, "", fmt.Errorf(
 			"create login client: %w", err,