feat(traces): add fold/unfold toggle button to JSON panels

[micookie2]

Summary

• Add a fold/unfold toggle button next to each JSON panel title (Raw Request, Raw Response, etc.) on the Traces page
• Clicking fold collapses all nested JSON levels while keeping the outermost { } visible
• Clicking again unfolds everything
• Useful for quickly inspecting top-level keys in large JSON payloads (e.g. prompt structure) without scrolling through deeply nested content

Changes

• Added editorRef to AccordionPanel to hold the Monaco Editor instance via onMount
• Added handleToggleFold: calls editor.foldAll then unfolds line 1 to keep the root object open
• Toggle button uses Minimize2/Maximize2 icons to indicate current state

Test plan

• Open the Traces page and click on a trace to view details
• Click the fold button next to Raw Request title — inner JSON should collapse, outermost { } stays visible
• Click again — all JSON should unfold
• Verify the copy button still works correctly