## Summary
Fixes the workflow show page being blank after the `styled(Component)`
removal in #18430.
- PR #18430 replaced `styled(PageBody)` with a plain `div` wrapper
(`StyledPageBodyForDesktopContainer`) around `PageBody`, but the wrapper
defaulted to `display: block`
- `PageBody`'s internal container uses `flex: 1 1 auto` to size itself,
which requires a flex parent — the block wrapper broke height
propagation, causing React Flow's container to have 0 height
- Added `display: flex; flex-direction: column` to both
`StyledPageBodyForDesktopContainer` and
`StyledPageBodyForMobileContainer` to restore the flex chain
## Test plan
- [x] Open a workflow record show page → diagram nodes are visible
- [x] Open a company/person record show page → fields, tabs, and content
render correctly
- [x] Lint and typecheck pass
Charles Bochet
e27a8b5107