feat(ui): align inventory + detail with mockups (seed icons, green theme)

Visual pass toward docs/mockups (06 inventory, 07 item):
- Bundle the seedks icon font (chars a–k → seed pictograms: jar, packet, spoon…)
  and a SeedGlyph/QuantityKindIcon helper.
- Green app bar + pale-green canvas theme (buildTaneTheme).
- Inventory list: rounded-square photo thumbnail or green initial avatar, bold
  title, scientific-name subtitle, trailing edit pencil, styled category
  headers, rounded search field, seed-glyph empty state.
- Quantity selectors (quick-add + add-lot) show the seed pictogram + word;
  detail lot lines use the kind's glyph.
- Detail header restyled to mockup 07: category link + scientific name on the
  left, photo on the right.

watchInventory now also returns the linked species' scientific name (subtitle).
37 app tests green; seedks font verified in the Linux asset bundle.

apps/app_seeds/lib/app.dart

@@ -9,6 +9,7 @@ import 'i18n/strings.g.dart';
 import 'state/inventory_cubit.dart';
 import 'state/variety_detail_cubit.dart';
 import 'ui/inventory_list_screen.dart';
+import 'ui/theme.dart';
 import 'ui/variety_detail_screen.dart';
 
 /// Root widget. Provides the repository + inventory cubit to the tree and wires
@@ -54,10 +55,7 @@ class TaneApp extends StatelessWidget {
       child: MaterialApp.router(
         onGenerateTitle: (context) => context.t.app.title,
         debugShowCheckedModeBanner: false,
-        theme: ThemeData(
-          colorSchemeSeed: const Color(0xFF4C7A34), // seed-green
-          useMaterial3: true,
-        ),
+        theme: buildTaneTheme(),
         locale: TranslationProvider.of(context).flutterLocale,
         supportedLocales: AppLocaleUtils.supportedLocales,
         localizationsDelegates: const [