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/pubspec.yaml

@@ -66,3 +66,8 @@ flutter:
   # Seed strings for slang live under lib/i18n (not a Flutter asset; compiled).
   assets:
     - assets/catalog/species.json
+  fonts:
+    # Custom seed-themed icon glyphs (chars a–k). See docs/mockups/seedks-glyphs.png.
+    - family: seedks
+      fonts:
+        - asset: fonts/seedks.ttf