feat: add evaluations UI with eval sets, runs, and evaluators

[cristipufu]

Summary

• Add full evaluations UI: eval sets (with I/O and evaluators tabs), eval runs (with score/I/O/logs tabs and trace tree), and evaluators management (create/edit forms, category filtering, card layout)
• Add backend support: eval data models, eval service, REST + WebSocket routes for eval sets, runs, and evaluators
• Restructure sidebar layout with shared header, activity bar, and section-specific content panels
• Add resizable split-pane layout with slide in/out animations, route-driven item selection, and auto-select on navigation
• Bump version to 0.0.61

Test plan

• Verify eval sets page loads with item grid, I/O and Evaluators tabs in sidebar
• Verify eval runs page shows results grid with score/I/O/logs tabs and trace tree
• Verify evaluators page with create/edit forms, category filtering, and card toggle
• Verify sidebar resize drag works smoothly without lag
• Verify sidebar slide in/out animations work on item selection/deselection
• Verify route-driven navigation and auto-select behavior
• Verify debug page is completely unchanged

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