feat(inventory): photo-first drafts + on-device OCR (digitization R2+R4)

Lower the bulk-digitization cliff with two more routes on top of the
already-landed CSV import and "save and add another":

- Photo-first drafts (capture now, catalogue later): burst-capture
  photos (camera or multi-gallery) into unnamed draft varieties, shown
  in a "to catalogue" tray, hidden from the main list until named.
  Adds Variety.isDraft (schema), addDraftVariety/watchDrafts/nameDraft,
  the triage sheet and the inventory banner.
- On-device OCR label suggestion (Tesseract, offline, no Google): a
  "Suggest name from photo" button in the naming dialog behind a
  LabelTextExtractor interface (Tesseract on Android/iOS, no-op
  elsewhere). Reads the largest print via hOCR bounding boxes, drops
  boilerplate/low-confidence noise, preprocesses (grayscale, contrast,
  upscale) and sweeps rotations (0-315 deg) so tilted packets still
  read. Bundles tessdata_fast eng+spa; validated on-device against real
  packets. The photo is written to a temp file deleted immediately in a
  finally block (the plugin needs a path) - a bounded, documented
  exception to no-plaintext-at-rest.

This commit also carries the co-developed schema evolution v5 to v8 that
shares these files (organic flag, species viability years, crop
calendar, lot provenance/abundance/preservation format, condition
checks) plus their exports/migrations and i18n.

Tests: CSV/draft/OCR unit + widget + migration green in isolation.
Note: the full widget suite currently hangs (>10 min) - under investigation.

apps/app_seeds/lib/services/onboarding_store.dart

@@ -0,0 +1,18 @@
+import '../security/secret_store.dart';
+
+/// Remembers whether the intro/onboarding carousel has been shown, so it only
+/// appears on first launch. Backed by the OS keystore (via [SecretStore]) to
+/// honour the "no plaintext at rest" rule — there is no shared_preferences here.
+class OnboardingStore {
+  OnboardingStore(this._store);
+
+  final SecretStore _store;
+
+  static const _introSeenKey = 'tane.intro_seen';
+
+  /// Whether the user has already seen (or skipped) the intro carousel.
+  Future<bool> introSeen() async => await _store.read(_introSeenKey) == '1';
+
+  /// Records that the intro has been shown; subsequent launches skip it.
+  Future<void> markIntroSeen() => _store.write(_introSeenKey, '1');
+}