By Rashika Singh and Joel Jose (Reuters) -Citigroup has raised its forecast for AI-related infrastructure spending by tech giants to surpass $2.8 trillion through 2029, from$2.3 trillion estimated earlier, citing aggressive early investments by hyperscalers and growing enterprise appetite. The AI boom ignited by ChatGPT's launch in late 2022 has continued to fuel staggering capital outlays and data center expansion despite a brief crisis of confidence sparked by China's cheaper DeepSeek model and linger ...