Co-managed buildings on the import review screen

PR #12781: the onboarding review screen now tells a company which of its AppFolio buildings are already set up under the company that owns them, and a company whose buildings are all like that can finish setup.

How this was captured: the branch dev server was run on the stage table, with an anonymous local session so the wizard reads no data. The wizard draft was seeded into the browser tab with made-up buildings, because the evidence tool cannot stage that storage and the demo import never produces this case. Each assertion below was checked in the page, not just in the picture.

Some buildings shared: 2 added, 3 already set up

• Asserted: the note reads exactly “3 buildings are already set up in PropFlow under the company that owns them. You manage them there, so we didn't add them again.”
• The line above still counts only what was added (2).

Every building shared: nothing new to add

• Asserted: “Nothing new to add. Press Continue if that looks right.” is shown, and “None of your buildings came in yet” is not.
• Critique round 1 used “Your buildings are already in PropFlow”, which repeated the note below it, so it was reworded. This is round 2.
• Left as is: the “Imported properties” card is empty. That is the existing behaviour for an import that added nothing, and it is accurate.

No shared buildings: unchanged

• Asserted: no note appears.