test(ui): small-phone overflow guard; fix Home clipping on small screens

Adds test/ui/small_screen_overflow_test.dart: pumps the full screens at a
320x568 (iPhone-SE-class) viewport in the longest-text locales (es/pt/ast);
a RenderFlex overflow fails the test, so a clipped title or save button is
caught. It found — and this fixes — a real bug: the Home menu (a fixed,
non-scrolling Center>Column) clipped ~80px on small phones in every locale.
Home is now wrapped in LayoutBuilder + SingleChildScrollView +
ConstrainedBox(minHeight: maxHeight): centered when it fits, scrolls when it
doesn't, never clipped.

Also makes the test harness faithful: wrapScreen/wrapDetail now map the
locale through materialLocaleFor (ast->es) exactly like the app, so Asturian
screens don't throw on MaterialLocalizations (AppBar tooltips) — that had
masqueraded as an overflow.

Scope notes in the test: full screens only (modal bottom sheets get an
unbounded height in widget tests -> false huge overflow; they already scroll
their body), and the variety-detail screen is skipped (its ~2px hit is on a
DISPOSED/DEFUNCT RenderFlex — a transient during the cubit rebuild, not the
stable layout).

apps/app_seeds/lib/ui/home_screen.dart

@@ -40,10 +40,18 @@ class HomeScreen extends StatelessWidget {
       body: Stack(
         children: [
           const Positioned.fill(child: _SeedWatermark()),
-          Center(
+          // Scroll when the menu doesn't fit a short screen (small phones), so
-            child: ConstrainedBox(
+          // the market card / buttons are never clipped; stays centered when it
-              constraints: const BoxConstraints(maxWidth: 440),
+          // does fit.
-              child: Padding(
+          LayoutBuilder(
+            builder: (context, constraints) => SingleChildScrollView(
+              child: ConstrainedBox(
+                constraints:
+                    BoxConstraints(minHeight: constraints.maxHeight),
+                child: Center(
+                  child: ConstrainedBox(
+                    constraints: const BoxConstraints(maxWidth: 440),
+                    child: Padding(
                 padding: const EdgeInsets.fromLTRB(24, 24, 24, 32),
                 child: Column(
                   mainAxisSize: MainAxisSize.min,
@@ -109,6 +117,9 @@ class HomeScreen extends StatelessWidget {
               ),
             ),
           ),
+                ),
+              ),
+            ),
         ],
       ),
     );

apps/app_seeds/test/support/test_support.dart

@@ -10,6 +10,7 @@ import 'package:tane/db/database.dart';
 import 'package:tane/i18n/strings.g.dart';
 import 'package:tane/security/secret_store.dart';
 import 'package:tane/services/onboarding_store.dart';
+import 'package:tane/app.dart' show materialLocaleFor;
 import 'package:tane/state/inventory_cubit.dart';
 import 'package:tane/state/variety_detail_cubit.dart';
 import 'package:tane/ui/variety_detail_screen.dart';
@@ -69,7 +70,7 @@ Widget wrapScreen({
       child: BlocProvider(
         create: (_) => InventoryCubit(repository),
         child: MaterialApp(
-          locale: locale.flutterLocale,
+          locale: materialLocaleFor(locale.flutterLocale),
           supportedLocales: AppLocaleUtils.supportedLocales,
           localizationsDelegates: const [
             GlobalMaterialLocalizations.delegate,
@@ -103,7 +104,7 @@ Widget wrapDetail({
       child: BlocProvider(
         create: (_) => VarietyDetailCubit(repository, varietyId),
         child: MaterialApp(
-          locale: locale.flutterLocale,
+          locale: materialLocaleFor(locale.flutterLocale),
           supportedLocales: AppLocaleUtils.supportedLocales,
           localizationsDelegates: const [
             GlobalMaterialLocalizations.delegate,

apps/app_seeds/test/ui/small_screen_overflow_test.dart

@@ -0,0 +1,115 @@
+import 'package:commons_core/commons_core.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/db/enums.dart';
+import 'package:tane/i18n/strings.g.dart';
+import 'package:tane/ui/home_screen.dart';
+import 'package:tane/ui/inventory_list_screen.dart';
+import 'package:tane/ui/settings_screen.dart';
+
+import '../support/test_support.dart';
+
+/// Small-phone layout guard. A Flutter `RenderFlex overflowed` (a clipped title,
+/// a save button pushed off a non-scrolling column, a Row too wide) is reported
+/// as an error and FAILS the test — so pumping each screen at a tiny viewport,
+/// in the languages whose text runs longest (es/pt/ast), catches exactly the
+/// "the save button / title isn't fully visible on a small phone" reports.
+///
+/// FULL SCREENS ONLY. Modal bottom sheets (quick-add, the lot editor) are NOT
+/// checked here: `showModalBottomSheet` gets an unbounded height in a widget
+/// test, which fabricates a huge false overflow. Those sheets already wrap their
+/// body in a `SingleChildScrollView`, so their save buttons stay reachable;
+/// verify them on a real small device.
+void main() {
+  // iPhone-SE-class logical viewport: narrow AND short, where clipping shows.
+  const small = Size(320, 568);
+  // The locales whose strings are longest — English rarely overflows first.
+  const longLocales = [AppLocale.es, AppLocale.pt, AppLocale.ast];
+
+  Future<void> pumpSmall(WidgetTester tester, Widget widget) async {
+    tester.view.physicalSize = small;
+    tester.view.devicePixelRatio = 1.0;
+    addTearDown(tester.view.resetPhysicalSize);
+    addTearDown(tester.view.resetDevicePixelRatio);
+    await tester.pumpWidget(widget);
+    await tester.pumpAndSettle();
+  }
+
+  for (final locale in longLocales) {
+    final tag = locale.languageCode;
+
+    testWidgets('home menu fits a small screen ($tag)', (tester) async {
+      final db = newTestDatabase();
+      addTearDown(db.close);
+      await pumpSmall(
+        tester,
+        wrapScreen(
+          repository: newTestRepository(db),
+          locale: locale,
+          child: const HomeScreen(marketEnabled: true),
+        ),
+      );
+      await disposeTree(tester);
+    });
+
+    testWidgets('settings (language, backup, about) fits ($tag)', (tester) async {
+      final db = newTestDatabase();
+      addTearDown(db.close);
+      await pumpSmall(
+        tester,
+        wrapScreen(
+          repository: newTestRepository(db),
+          locale: locale,
+          child: const SettingsScreen(),
+        ),
+      );
+      await disposeTree(tester);
+    });
+  }
+
+  testWidgets('inventory (empty) fits a small screen', (tester) async {
+    final db = newTestDatabase();
+    addTearDown(db.close);
+    await pumpSmall(
+      tester,
+      wrapScreen(
+        repository: newTestRepository(db),
+        locale: AppLocale.es,
+        child: const InventoryListScreen(),
+      ),
+    );
+    await disposeTree(tester);
+  });
+
+  testWidgets('inventory with a long-named seed fits a small screen',
+      (tester) async {
+    final db = newTestDatabase();
+    addTearDown(db.close);
+    final repo = newTestRepository(db);
+    final id = await repo.addQuickVariety(
+      label: 'Tomate rosa de Barbastro extraordinariamente larguísimo',
+      category: 'Solanáceas',
+    );
+    await repo.addLot(
+      varietyId: id,
+      harvestYear: 2024,
+      quantity: const Quantity(kind: QuantityKind.handful),
+      offerStatus: OfferStatus.shared,
+    );
+    await pumpSmall(
+      tester,
+      wrapScreen(
+        repository: repo,
+        locale: AppLocale.es,
+        child: const InventoryListScreen(),
+      ),
+    );
+    await disposeTree(tester);
+  });
+
+  // NOTE: the variety-detail screen is deliberately NOT overflow-checked here.
+  // It reports a ~2px overflow on a RenderFlex that is already DISPOSED/DEFUNCT
+  // — a transient stale frame while its cubit's Drift stream rebuilds during
+  // pumpAndSettle, not the stable rendered layout. Guarding it would be flaky;
+  // its RTL/build coverage lives in rtl_smoke_test.dart.
+}