Property address now on estimate cover, preview scrolling fixed

Estimate covers now display property address under the client name. Preview layout no longer scrolls the document body.

Features

Property address on cover page: The estimate cover page now displays the property address under the client name in the "Prepared for" section. This gives readers the address context immediately without scrolling to the footer.

Bug Fixes

Preview scrolling: After the preview moved into the app shell, the document body was still scrolling even though the sidebar and top bar were visible. The preview layout now pins itself to exactly the remaining viewport height (100svh − 3.5rem for the top bar), preventing unwanted document scroll while the editor and spreadsheet panels scroll independently.