feat: fix project status counts, add top pagination and sortable columns

- Status counts now show each project's latest round state only
  (no more inflated counts from projects passing multiple rounds)
- Add pagination controls at top of projects, members, and observer lists
- Add sortable column headers to admin projects table (title, category,
  program, assignments, status) and members table (name, role, status,
  last login)
- Backend: add sortBy/sortDir params to project.list and user.list

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/shared/sortable-header.tsx

@@ -0,0 +1,45 @@
+'use client'
+
+import { TableHead } from '@/components/ui/table'
+import { cn } from '@/lib/utils'
+import { ArrowUpDown, ArrowUp, ArrowDown } from 'lucide-react'
+
+type SortableHeaderProps = {
+  label: string
+  column: string
+  currentSort?: string
+  currentDir?: 'asc' | 'desc'
+  onSort: (column: string) => void
+  className?: string
+}
+
+export function SortableHeader({
+  label,
+  column,
+  currentSort,
+  currentDir,
+  onSort,
+  className,
+}: SortableHeaderProps) {
+  const isActive = currentSort === column
+
+  return (
+    <TableHead
+      className={cn('cursor-pointer select-none hover:bg-muted/50 transition-colors', className)}
+      onClick={() => onSort(column)}
+    >
+      <div className="flex items-center gap-1">
+        {label}
+        {isActive ? (
+          currentDir === 'asc' ? (
+            <ArrowUp className="h-3.5 w-3.5 text-foreground" />
+          ) : (
+            <ArrowDown className="h-3.5 w-3.5 text-foreground" />
+          )
+        ) : (
+          <ArrowUpDown className="h-3.5 w-3.5 text-muted-foreground/50" />
+        )}
+      </div>
+    </TableHead>
+  )
+}