feat: AI assistant widget, design system upgrade via 21st-dev Magic
Backend:
- Add AI assistant service with gap detection, anomaly analysis, Anthropic tool_use streaming
- Add assistant router (chat SSE, history, flags CRUD, session categorization)
- Fix agentic loop: text+tool_use in single assistant message per Anthropic spec
- Migrate logging from stdlib to structlog in assistant modules
- Fix migration 0005: UUID type for ai_flags/assistant_messages FKs
Frontend:
- Fix vite base path → /cc-dashboard/static/ to match FastAPI StaticFiles mount
- Redesign Sidebar: gradient background, amber gradient active state, 44px touch targets, user avatar
- Redesign KpiCard: corner decorations, ring border, trend icon, baseline bar (21st.dev pattern)
- Redesign TopBar: backdrop-blur, sticky, gradient user avatar, sign-out button
- Improve AssistantWidget: fix setInterval leak, aria-labels, proper markdown block parser
- Fix AssistantWidget renderMarkdown: line-by-line parser for correct list/header nesting
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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