feat: implement full admin panel with dashboard, user management, and platform settings

Adds complete super_admin panel with 9 pages and account owner categories page.
Backend includes 5 new DB tables, ~25 API endpoints, settings manager with
in-memory cache, and 29 integration tests. Frontend includes reusable admin
components (DataTable, Pagination, ActionMenu, etc.) with code-split lazy loading.

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

frontend/src/components/admin/SearchInput.tsx

@@ -0,0 +1,66 @@
+import { useState, useEffect, useRef, useCallback } from 'react'
+import { Search, X } from 'lucide-react'
+import { debounce } from 'lodash'
+import { cn } from '@/lib/utils'
+
+interface SearchInputProps {
+  value?: string
+  onSearch: (value: string) => void
+  placeholder?: string
+  className?: string
+}
+
+export function SearchInput({ value = '', onSearch, placeholder = 'Search...', className }: SearchInputProps) {
+  const [localValue, setLocalValue] = useState(value)
+  const debouncedRef = useRef<ReturnType<typeof debounce> | null>(null)
+
+  useEffect(() => {
+    setLocalValue(value)
+  }, [value])
+
+  useEffect(() => {
+    debouncedRef.current = debounce((v: string) => {
+      onSearch(v)
+    }, 300)
+    return () => {
+      debouncedRef.current?.cancel()
+    }
+  }, [onSearch])
+
+  const handleChange = useCallback((e: React.ChangeEvent<HTMLInputElement>) => {
+    const v = e.target.value
+    setLocalValue(v)
+    debouncedRef.current?.(v)
+  }, [])
+
+  const handleClear = () => {
+    setLocalValue('')
+    onSearch('')
+  }
+
+  return (
+    <div className={cn('relative', className)}>
+      <Search className="absolute left-3 top-1/2 h-4 w-4 -translate-y-1/2 text-muted-foreground" />
+      <input
+        type="text"
+        value={localValue}
+        onChange={handleChange}
+        placeholder={placeholder}
+        className={cn(
+          'h-9 w-full rounded-md border border-border bg-background pl-9 pr-8 text-sm',
+          'placeholder:text-muted-foreground focus:outline-none focus:ring-2 focus:ring-ring'
+        )}
+      />
+      {localValue && (
+        <button
+          onClick={handleClear}
+          className="absolute right-2 top-1/2 -translate-y-1/2 rounded p-0.5 text-muted-foreground hover:text-foreground"
+        >
+          <X className="h-3.5 w-3.5" />
+        </button>
+      )}
+    </div>
+  )
+}
+
+export default SearchInput