Home page:
- Centered hero with app description and purpose
- Richer dataset cards with metadata badges and start date
- File lookup embedded directly on home (date + time pickers)

Dashboard:
- Replaced verbose 'Global Controls' card with compact single-row
  filter toolbar: date range, granularity pill buttons, router
  toggles, and reset - all inline
- Removed redundant page heading (dataset shown in header breadcrumb)
- MetricSelector is now collapsible - shows summary when closed,
  expands to reveal quick-select tabs and checkbox grid

File Lookup (/netflow/files):
- Replaced raw 12-digit timestamp input with proper date picker and
  5-minute-interval time dropdown
- Centered card layout with clear purpose description
- Eliminated jargon (YYYYMMDDHHmm format)

Header:
- Removed redundant 'Home' nav link (logo serves that purpose)
- Added dataset breadcrumb when viewing a dataset page
- Renamed 'Files' to 'File Lookup' for clarity
- Slimmer 48px header height

Co-authored-by: oliver <flamboh@users.noreply.github.com>