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/seed_glyph.dart

@@ -0,0 +1,87 @@
+import 'package:commons_core/commons_core.dart';
+import 'package:flutter/material.dart';
+
+/// Renders a glyph from the bundled `seedks` icon font, whose characters `a`–`k`
+/// map to seed-themed pictograms (jar, packet, spoon…). See
+/// docs/mockups/seedks-glyphs.png.
+class SeedGlyph extends StatelessWidget {
+  const SeedGlyph(this.char, {this.size = 24, this.color, super.key});
+
+  final String char;
+  final double size;
+  final Color? color;
+
+  @override
+  Widget build(BuildContext context) {
+    return Text(
+      char,
+      style: TextStyle(
+        fontFamily: 'seedks',
+        fontSize: size,
+        height: 1,
+        color: color ?? Theme.of(context).colorScheme.primary,
+      ),
+    );
+  }
+}
+
+/// Named seedks glyphs (the character each pictogram is mapped to).
+abstract final class SeedGlyphs {
+  static const jar = 'a';
+  static const jars = 'b';
+  static const search = 'c';
+  static const share = 'd';
+  static const sack = 'e';
+  static const smallSpoon = 'f';
+  static const bigSpoon = 'g';
+  static const mug = 'h';
+  static const envelope = 'i';
+  static const pouring = 'j';
+  static const scattered = 'k';
+}
+
+/// The seedks character for a quantity [kind], or null for plant-form/precise
+/// kinds that have no seed pictogram (they fall back to a Material icon).
+String? seedGlyphForKind(QuantityKind kind) => switch (kind) {
+  QuantityKind.aFew => SeedGlyphs.scattered,
+  QuantityKind.some => SeedGlyphs.smallSpoon,
+  QuantityKind.plenty => SeedGlyphs.jars,
+  QuantityKind.handful => SeedGlyphs.bigSpoon,
+  QuantityKind.pinch => SeedGlyphs.scattered,
+  QuantityKind.jar => SeedGlyphs.jar,
+  QuantityKind.packet => SeedGlyphs.envelope,
+  _ => null,
+};
+
+IconData _materialIconForKind(QuantityKind kind) => switch (kind) {
+  QuantityKind.grams => Icons.scale_outlined,
+  QuantityKind.count => Icons.tag,
+  QuantityKind.cob || QuantityKind.ear => Icons.grass,
+  QuantityKind.head || QuantityKind.seedHead => Icons.filter_vintage_outlined,
+  QuantityKind.fruit => Icons.local_florist_outlined,
+  QuantityKind.bulb ||
+  QuantityKind.tuber ||
+  QuantityKind.bunch => Icons.spa_outlined,
+  _ => Icons.eco_outlined,
+};
+
+/// A consistent icon for a [QuantityKind]: the seed glyph where one exists,
+/// otherwise a Material fallback.
+class QuantityKindIcon extends StatelessWidget {
+  const QuantityKindIcon(this.kind, {this.size = 24, this.color, super.key});
+
+  final QuantityKind kind;
+  final double size;
+  final Color? color;
+
+  @override
+  Widget build(BuildContext context) {
+    final glyph = seedGlyphForKind(kind);
+    if (glyph != null) return SeedGlyph(glyph, size: size, color: color);
+    return Icon(
+      _materialIconForKind(kind),
+      size: size,
+      color: color ?? Theme.of(context).colorScheme.primary,
+    );
+  }
+}