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/expenses/expense-detail.tsx

@@ -75,7 +75,7 @@ function ReceiptThumbnail({ fileId }: { fileId: string }) {
       <div className="mt-2 flex items-center justify-between text-xs text-muted-foreground">
         <span className="truncate">{mime || (isError ? 'Receipt' : 'File')}</span>
         <a
-          href={`/api/v1/files/${fileId}/download`}
+          href={`/api/v1/files/${fileId}/download?redirect=1`}
           className="inline-flex items-center gap-1 text-primary hover:underline"
         >
           <Download className="h-3 w-3" aria-hidden /> Download