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/ui/quick_add_sheet.dart

@@ -9,6 +9,7 @@ import '../data/variety_repository.dart';
 import '../i18n/strings.g.dart';
 import '../state/quick_add_cubit.dart';
 import 'quantity_kind_l10n.dart';
+import 'seed_glyph.dart';
 
 /// Picks a photo and returns its bytes (or null if cancelled). Injected so
 /// widget tests can supply a fake instead of the camera plugin.
@@ -103,6 +104,7 @@ class QuickAddSheet extends StatelessWidget {
                 children: [
                   for (final kind in _quickKinds)
                     ChoiceChip(
+                      avatar: QuantityKindIcon(kind, size: 18),
                       label: Text(quantityKindLabel(t, kind)),
                       selected: state.quantityKind == kind,
                       onSelected: (_) => cubit.selectQuantity(kind),