style(ui): float remaining table/card containers to design system

Repo-wide sweep for the same flat 1px-border "fake card" pattern
already fixed in Dashboard/Kanban/JobDetailsDialog/auth pages this
session -- AddJobModal, Attachments, CompaniesTable, Correspondence,
EditJobDialog, and the admin audit/system/users pages all had a table
container or content box using border+divider instead of the
floating-shadow treatment used everywhere else now.

Left AppShell.tsx/App.tsx alone -- their border:1px+divider instances
are icon-button and badge outlines, not card containers; that's a
different, correct use of the pattern.

job-tracker-ui/src/components/Attachments.tsx

@@ -267,7 +267,7 @@ export default function Attachments({ jobId }: { jobId: number }) {
         {uploading ? <LinearProgress sx={{ mt: 1.5, borderRadius: 999 }} /> : null}
       </Box>
 
-      <TableContainer sx={{ borderRadius: 3, border: "1px solid", borderColor: "divider" }}>
+      <TableContainer sx={{ borderRadius: 3, border: "none", boxShadow: "0px 1px 2px 0px rgba(15,23,42,0.04), 0px 8px 24px -12px rgba(15,23,42,0.12)" }}>
         <Table size="small">
           <TableHead>
             <TableRow>