feat(stash): password strength meter + filename hint on encrypted export

- Export dialog shows a 4-segment strength meter (length + character classes)
  with a Weak/Fair/Good/Strong label as you type the password.
- Shows the filename that will be saved; encrypted exports get an
  '-encrypted' suffix so the file is self-describing at a glance.

src/components/StashBackupDialogs.tsx

@@ -10,17 +10,40 @@ import { cn } from '@/lib/utils';
 
 type ExportMode = 'password' | 'nip44' | 'plaintext';
 
+/** Cheap password-strength heuristic (length + character classes), 0–4. */
+function passwordStrength(pw: string): number {
+  if (!pw) return 0;
+  let score = 0;
+  if (pw.length >= 8) score++;
+  if (pw.length >= 12) score++;
+  if (/[a-z]/.test(pw) && /[A-Z]/.test(pw)) score++;
+  if (/\d/.test(pw)) score++;
+  if (/[^A-Za-z0-9]/.test(pw)) score++;
+  return Math.min(4, score);
+}
+
+const STRENGTH_STEPS = [
+  { key: 'walletUi.stash.strengthWeak', bar: 'bg-red-500', text: 'text-red-400' },
+  { key: 'walletUi.stash.strengthWeak', bar: 'bg-red-500', text: 'text-red-400' },
+  { key: 'walletUi.stash.strengthFair', bar: 'bg-amber-500', text: 'text-amber-400' },
+  { key: 'walletUi.stash.strengthGood', bar: 'bg-lime-500', text: 'text-lime-400' },
+  { key: 'walletUi.stash.strengthStrong', bar: 'bg-green-500', text: 'text-green-400' },
+] as const;
+
 /** Export the stash as a file, optionally password- or key-protected. */
 export function StashBackupExportDialog({
   open,
   onOpenChange,
   itemCount,
+  baseName,
   canUseKey,
   onExport,
 }: {
   open: boolean;
   onOpenChange: (open: boolean) => void;
   itemCount: number;
+  /** Filename without extension, e.g. `skatespots-stash-2026-10-03`. */
+  baseName: string;
   canUseKey: boolean;
   onExport: (opts: { mode: ExportMode; password?: string }) => Promise<void>;
 }) {
@@ -32,6 +55,12 @@ export function StashBackupExportDialog({
   const [busy, setBusy] = useState(false);
   const [error, setError] = useState<string | null>(null);
 
+  const strength = passwordStrength(pw);
+  const step = STRENGTH_STEPS[strength];
+  // The main button always produces an encrypted file; the plaintext link is a
+  // separate, explicit action.
+  const previewName = `${baseName}-encrypted.json`;
+
   useEffect(() => {
     if (open) {
       setMode('password');
@@ -133,6 +162,19 @@ export function StashBackupExportDialog({
                 />
               </div>
               <p className="text-[11px] leading-snug text-gray-500">{t('walletUi.stash.passwordHint')}</p>
+              {pw.length > 0 && (
+                <div className="space-y-1">
+                  <div className="flex items-center justify-between text-[10px] uppercase tracking-wide">
+                    <span className="text-gray-500">{t('walletUi.stash.strength')}</span>
+                    <span className={step.text}>{t(step.key)}</span>
+                  </div>
+                  <div className="flex gap-1">
+                    {[0, 1, 2, 3].map((i) => (
+                      <span key={i} className={cn('h-1 flex-1 rounded-full', i < strength ? step.bar : 'bg-white/10')} />
+                    ))}
+                  </div>
+                </div>
+              )}
             </div>
           ) : (
             <p className="text-xs text-gray-400">{t('walletUi.stash.keyModeHint')}</p>
@@ -143,6 +185,10 @@ export function StashBackupExportDialog({
               <AlertTriangle className="mt-0.5 h-3.5 w-3.5 shrink-0" /> {error}
             </p>
           )}
+
+          <p className="text-center font-mono text-[10px] text-gray-500">
+            {t('walletUi.stash.filenameWillSave', { name: previewName })}
+          </p>
         </div>
 
         <DialogFooter className="flex-col gap-2 sm:flex-col">

src/i18n/en.ts

@@ -6324,6 +6324,12 @@ walletUi: {
       unlockFailed: 'Could not unlock the backup.',
       show: 'Show',
       hide: 'Hide',
+      strength: 'Password strength',
+      strengthWeak: 'Weak',
+      strengthFair: 'Fair',
+      strengthGood: 'Good',
+      strengthStrong: 'Strong',
+      filenameWillSave: 'Will save as {{name}}',
       export: 'Export',
       import: 'Import',
       exported: 'Stash exported',

src/i18n/es.ts

@@ -6324,6 +6324,12 @@ walletUi: {
       unlockFailed: 'No se pudo desbloquear la copia.',
       show: 'Mostrar',
       hide: 'Ocultar',
+      strength: 'Seguridad de la contraseña',
+      strengthWeak: 'Débil',
+      strengthFair: 'Aceptable',
+      strengthGood: 'Buena',
+      strengthStrong: 'Fuerte',
+      filenameWillSave: 'Se guardará como {{name}}',
       export: 'Exportar',
       import: 'Importar',
       exported: 'Stash exportado',

src/pages/StashPage.tsx

@@ -662,6 +662,7 @@ export default function StashPage() {
   const [exportOpen, setExportOpen] = useState(false);
   const [unlockOpen, setUnlockOpen] = useState(false);
   const [importParsed, setImportParsed] = useState<unknown>(null);
+  const exportBaseName = `skatespots-stash-${new Date().toISOString().slice(0, 10)}`;
 
   // ── Backup & transfer: your stash is encrypted on Nostr, but a local copy you
   // control means a dead relay (or a new account) can't lose your gear list. ──
@@ -677,7 +678,7 @@ export default function StashPage() {
     const url = URL.createObjectURL(blob);
     const a = document.createElement('a');
     a.href = url;
-    a.download = `skatespots-stash-${new Date().toISOString().slice(0, 10)}.json`;
+    a.download = `${exportBaseName}${mode === 'plaintext' ? '' : '-encrypted'}.json`;
     document.body.appendChild(a);
     a.click();
     a.remove();
@@ -1567,6 +1568,7 @@ export default function StashPage() {
         open={exportOpen}
         onOpenChange={setExportOpen}
         itemCount={items.length}
+        baseName={exportBaseName}
         canUseKey={!!user?.signer?.nip44}
         onExport={handleExport}
       />