Refine frontend UI and query workflow

[seanqsun]

Summary

• refine the application chrome, environment-aware navigation, spacing, typography, colors, and shared interaction patterns
• redesign the dashboard and login experience, add richer activity charts, and provide removable development mock data for local review
• add a no-code SQL query builder with improved targeting controls and platform brand marks
• standardize status, tag, filter, selection, and metadata chip semantics across the frontend

Testing

• npm test -- --run (40 files, 273 tests)
• npm run build
• go test ./...
• npm audit --omit=dev