feat(uat): file preview/download fix, clients-by-country page, residential column picker

Batch #4 UAT items.

1. Documents — clicking any file dumped raw presigned-URL JSON. Was
   systemic: 6 surfaces linked a browser directly at the JSON-returning
   /files/[id]/{download,preview} routes. Those routes now 302-redirect
   when called with ?redirect=1 (default stays JSON for the dialog +
   interest-eoi-tab programmatic consumers); the six <Link> sites use it.
   The documents-hub file row now opens the inline FilePreviewDialog +
   has a per-row Download button, and the preview dialog header gained a
   persistent Download button for all file types.

2. Clients-by-country — the widget's "+N more" dead text is now a
   "Show all" link to a new /clients/by-country page rendering the full
   ranked country breakdown (each row drills into the filtered list).

3. Residential clients list — moved off its bespoke table onto the
   shared DataTable + ColumnPicker (same UX as clients/interests). Adds
   a "Date added" column, default-hides the empty "Residence" column,
   preserves the mobile card view, persists per-user column choices.

tsc clean, eslint clean, 1584/1584 vitest.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/invoices/invoice-card.tsx

@@ -105,7 +105,10 @@ export function InvoiceCard({
             </DropdownMenuItem>
             {invoice.pdfFileId ? (
               <DropdownMenuItem asChild>
-                <Link href={`/api/v1/files/${invoice.pdfFileId}/preview`} target="_blank">
+                <Link
+                  href={`/api/v1/files/${invoice.pdfFileId}/preview?redirect=1`}
+                  target="_blank"
+                >
                   <FileText className="mr-2 h-3.5 w-3.5" />
                   View PDF
                 </Link>