feat(block1): inventory walking skeleton + first quick-add slice

Stand up the Tanemaki monorepo and the first end-to-end vertical slice of
Block 1 (offline, encrypted inventory): add a seed → see it in a categorized,
searchable list → it persists → reopen and it's still there.

Architecture (state management like G1nkgo, adapted to Tane's reality):
- flutter_bloc (Cubit-first), but the encrypted Drift DB is the single source
  of truth; cubits stream from repositories (no hydrated_bloc/Hive, which would
  write plaintext at rest).
- get_it composition root; go_router; slang i18n (ES/EN, Weblate-friendly JSON).

Workspace & core:
- pub workspace: packages/commons_core (pure Dart) + apps/app_seeds (Flutter).
- commons_core primitives: UUIDv7 IdGen, Hybrid Logical Clock, Quantity value
  type (+ plant-aware QuantityKind), IdentityService root-seed stub.

Data & security:
- Drift schemaVersion=1 with all 10 Block-1 tables + common CRDT columns
  (HLC updated_at, last_author, tombstones); Movement append-only.
- SQLCipher via an injectable executor that refuses to open a plaintext DB;
  DB key + root seed in the OS keystore (separate secrets).
- Exported drift_schema_v1.json + migration scaffold.

Tests (near-TDD; nothing merges without tests):
- commons_core units (24), Drift migration test, "no plaintext at rest"
  security guard (runs where SQLCipher is present, skips otherwise),
  repository, widget, full quick-add flow, file-reopen persistence, and a
  no-hardcoded-strings i18n guard. GitLab CI: format + analyze + test + coverage.

Follow-on Block-1 stories (item detail/edit, species catalog, germination UI)
and all of Block 2 remain out of scope.

packages/commons_core/lib/src/value/quantity.dart

@@ -0,0 +1,67 @@
+import 'package:equatable/equatable.dart';
+
+/// Coarse groups used by the UI to suggest relevant [QuantityKind]s for a
+/// species/family. Purely presentational — never forces a choice.
+enum QuantityGroup { informal, plantForm, precise }
+
+/// A stable, extensible, i18n vocabulary for *rough, human* seed amounts.
+///
+/// Values go deliberately beyond kitchen measures: seeds are counted in the
+/// forms the plant gives them (a cob, a pod, a flower head…). The display label
+/// is localized from [name] — so the enum name is the stable storage key and
+/// must never be renumbered or reused (see data-model §5 migration rules).
+enum QuantityKind {
+  // Informal / generic
+  aFew(QuantityGroup.informal),
+  some(QuantityGroup.informal),
+  plenty(QuantityGroup.informal),
+  handful(QuantityGroup.informal),
+  pinch(QuantityGroup.informal),
+  jar(QuantityGroup.informal),
+  packet(QuantityGroup.informal),
+  // Plant-form natural units
+  cob(QuantityGroup.plantForm),
+  head(QuantityGroup.plantForm),
+  pod(QuantityGroup.plantForm),
+  ear(QuantityGroup.plantForm),
+  fruit(QuantityGroup.plantForm),
+  bulb(QuantityGroup.plantForm),
+  tuber(QuantityGroup.plantForm),
+  seedHead(QuantityGroup.plantForm),
+  bunch(QuantityGroup.plantForm),
+  // Precise
+  grams(QuantityGroup.precise),
+  count(QuantityGroup.precise);
+
+  const QuantityKind(this.group);
+
+  final QuantityGroup group;
+}
+
+/// A quantity held or moved: a qualitative [kind], plus an optional [precise]
+/// amount (grams / seed count) and an optional free-text [label] for rough
+/// amounts no [kind] captures. Shared value type used by both Lot and Movement.
+class Quantity extends Equatable {
+  const Quantity({required this.kind, this.precise, this.label});
+
+  final QuantityKind kind;
+
+  /// Optional precise amount, meaningful for [QuantityGroup.precise] kinds.
+  final double? precise;
+
+  /// Optional free text ("half a jam jar") when no [kind] fits well.
+  final String? label;
+
+  bool get isPrecise => precise != null;
+
+  Quantity copyWith({QuantityKind? kind, double? precise, String? label}) {
+    return Quantity(
+      kind: kind ?? this.kind,
+      precise: precise ?? this.precise,
+      label: label ?? this.label,
+    );
+  }
+
+  @override
+  List<Object?> get props => [kind, precise, label];
+}