fix(app): keep a tall dialog's footer reachable and unstick acceptance

DialogContent is fixed and centre-translated, so a page cannot scroll to
it. Without a height cap a dialog taller than the viewport hung its own
footer off-screen: the submit button rendered, reported visible and
enabled, and could never be clicked. Playwright burned a 300s timeout
retrying it 522 times on the upload tab of Create fleet library, which is
the first dialog to cross 720px — a real operator on a laptop was just as
stuck. Cap the panel at the viewport and scroll inside it; dialogs that
already fit are unaffected.

Three acceptance specs still clicked the workspace submit by the copy
c6819ed4c renamed (Create workspace -> Create), and removeUploadedFleet
addressed ConfirmDialog through getByRole("dialog") when it renders
role="alertdialog". That second one had never run: the viewport timeout
died first and hid it.

Together these are what cancelled acceptance-e2e-dev at its 10-minute
budget on every run since Aug 20. The operator-catalog project goes from
34.6m to 5.5m, 21/21.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>