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/handlers/auth.go

@@ -94,14 +94,16 @@ func (hdlr *Handlers) executeRegister(
 	request *http.Request,
 	nick, password, username string,
 ) {
+	remoteIP := clientIP(request)
+
 	hostname := resolveHostname(
-		request.Context(), clientIP(request),
+		request.Context(), remoteIP,
 	)
 
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.RegisterUser(
 			request.Context(),
-			nick, password, username, hostname,
+			nick, password, username, hostname, remoteIP,
 		)
 	if err != nil {
 		hdlr.handleRegisterError(
@@ -196,11 +198,18 @@ func (hdlr *Handlers) handleLogin(
 		return
 	}
 
+	remoteIP := clientIP(request)
+
+	hostname := resolveHostname(
+		request.Context(), remoteIP,
+	)
+
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.LoginUser(
 			request.Context(),
 			payload.Nick,
 			payload.Password,
+			remoteIP, hostname,
 		)
 	if err != nil {
 		hdlr.respondError(