feat: embed real-time backend log terminal with persistent streaming support

[beraterkek-kafein]

• capture Python stdout, stderr, and system logger output through a global log handler
• normalize multiline log messages for Server-Sent Events stream compatibility
• stream backend console logs to the canvas through a native EventSource connection
• add a draggable and resizable terminal panel with persistent log buffering and scroll state
• reposition chat controls and zoom actions dynamically to accommodate terminal visibility
• optimize resize interactions to eliminate transition delays during drag operations
• support IDE-style log search with match case, whole word, regex, and sequential navigation
• preserve layout stability while highlighting search matches to prevent text shifting
• simplify configuration fallback handling and surface missing configuration errors in logs
• correct LangSmith configuration detection by evaluating boolean string values