feat(ux): usable amounts, colour-coded category/form chips, currency quick-picks

Four usability passes across the everyday flows:

- Quantity picker: a countable unit (cob/pod/ear…) now defaults to 1 and
  the stepper clamps at a minimum of 1 — you can never store 'a cob' with
  a blank/zero figure. Vibe units (a few) still carry no number.
- Category & form chips are colour-coded (new category_palette.dart): a
  small muted earthy palette maps each botanical family to a STABLE
  tonality (fill + readable ink), and each lot form gets its own tone.
  Applied to the inventory filter bar (now grouped attributes | forms |
  families, separated by a hairline), the list's category headers (a
  matching colour dot), and the lot-form selector.
- Sale currency: quick-pick chips (€ · Ğ1 · hours) fill the field in one
  tap — Ğ1 offered quietly among familiar options, never imposed — while
  free text still takes anything else. New i18n key sale.hours (en/es/pt/ast).

Tests: quantity_picker_test (default-1, clamp, vibe, clear-still-1),
category_palette_test (stable/distinct swatches); overflow guard + the
inventory widget tests stay green.

apps/app_seeds/lib/ui/quantity_picker.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 
 import '../db/enums.dart';
 import '../i18n/strings.g.dart';
+import 'category_palette.dart';
 import 'quantity_kind_l10n.dart';
 import 'seed_glyph.dart';
 import 'theme.dart';
@@ -76,18 +77,28 @@ class LotTypeSelector extends StatelessWidget {
       runSpacing: 8,
       children: [
         for (final type in LotType.values)
-          ChoiceChip(
-            key: Key('lotType.${type.name}'),
-            selected: value == type,
-            onSelected: (_) => onChanged(type),
-            avatar: type == LotType.seed
-                ? const SeedGlyph(SeedGlyphs.jars, size: 18)
-                : Icon(iconForLotType(type), size: 18),
-            label: Text(lotTypeLabel(t, type)),
-          ),
+          _buildTypeChip(t, type),
       ],
     );
   }
+
+  Widget _buildTypeChip(Translations t, LotType type) {
+    final swatch = lotTypeSwatch(type);
+    final selected = value == type;
+    return ChoiceChip(
+      key: Key('lotType.${type.name}'),
+      selected: selected,
+      onSelected: (_) => onChanged(type),
+      avatar: type == LotType.seed
+          ? const SeedGlyph(SeedGlyphs.jars, size: 18)
+          : Icon(iconForLotType(type), size: 18, color: swatch.ink),
+      label: Text(lotTypeLabel(t, type)),
+      backgroundColor: swatch.fill,
+      selectedColor: swatch.ink.withValues(alpha: 0.24),
+      side: BorderSide(color: swatch.ink.withValues(alpha: 0.35)),
+      labelStyle: TextStyle(color: swatch.ink, fontWeight: FontWeight.w500),
+    );
+  }
 }
 
 /// Optional packaging selector for living lots. Tapping the selected chip again
@@ -189,19 +200,29 @@ class _QuantityPickerState extends State<QuantityPicker> {
       widget.onChanged(null);
       return;
     }
-    final n = num.tryParse(_countController.text.trim().replaceAll(',', '.'));
-    widget.onChanged(Quantity(kind: kind, count: kind.countable ? n : null));
+    // A countable unit always carries a number ≥ 1 — "3 cobs", never an empty
+    // "cob". Blank/zero/garbage while typing falls back to 1, so you can never
+    // save a countable amount with no figure.
+    final parsed = num.tryParse(_countController.text.trim().replaceAll(',', '.'));
+    final count = kind.countable ? ((parsed == null || parsed < 1) ? 1 : parsed) : null;
+    widget.onChanged(Quantity(kind: kind, count: count));
   }
 
   void _select(QuantityKind kind) {
-    setState(() => _kind = kind);
+    setState(() {
+      _kind = kind;
+      // Selecting a countable unit with no number yet defaults it to 1.
+      if (kind.countable && (num.tryParse(_countController.text.trim()) == null)) {
+        _countController.text = '1';
+      }
+    });
     _emit();
   }
 
   void _bump(int delta) {
-    final current = int.tryParse(_countController.text.trim()) ?? 0;
-    final next = (current + delta).clamp(0, 9999);
-    _countController.text = next == 0 ? '' : '$next';
+    final current = int.tryParse(_countController.text.trim()) ?? 1;
+    final next = (current + delta).clamp(1, 9999);
+    _countController.text = '$next';
     _emit();
   }
 
@@ -219,6 +240,7 @@ class _QuantityPickerState extends State<QuantityPicker> {
           children: [
             for (final kind in kinds)
               _ScaleItem(
+                key: Key('quantity.kind.${kind.name}'),
                 kind: kind,
                 label: unitLabel(t, kind),
                 selected: _kind == kind,
@@ -273,6 +295,7 @@ class _ScaleItem extends StatelessWidget {
     required this.label,
     required this.selected,
     required this.onTap,
+    super.key,
   });
 
   final QuantityKind kind;