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/domain/seed_viability.dart

@@ -0,0 +1,41 @@
+/// Viability status of a seed lot, derived purely from its age versus the
+/// species' typical seed longevity (bundled reference data). Turns passive
+/// storage into active stewardship: it surfaces which lots to sow or regenerate
+/// before they lapse, instead of just accumulating them.
+enum SeedViability {
+  /// Comfortably within the species' typical viability window.
+  fresh,
+
+  /// In the final year of the window — sow or reproduce this season.
+  expiringSoon,
+
+  /// Past the typical viability window — germination is likely dropping fast.
+  expired,
+
+  /// Not enough data to judge (no harvest year, or no reference figure).
+  unknown,
+}
+
+/// Computes the viability status of a seed lot harvested in [harvestYear] for a
+/// species whose typical longevity is [viabilityYears], as of [currentYear].
+///
+/// A conservative, age-based signal: the bundled figure is a single number, not
+/// a decay curve, so this only distinguishes "fine / use soon / past it".
+/// [expiringSoon] flags the last year of the window so the grower can prioritise
+/// what to reproduce before it lapses. Any actual [GerminationTest] a grower
+/// records remains the ground truth and is shown alongside this estimate.
+SeedViability seedViability({
+  required int? harvestYear,
+  required int? viabilityYears,
+  required int currentYear,
+}) {
+  if (harvestYear == null || viabilityYears == null || viabilityYears <= 0) {
+    return SeedViability.unknown;
+  }
+  final age = currentYear - harvestYear;
+  // A harvest stamped in the future is treated as fresh, not expired.
+  if (age < 0) return SeedViability.fresh;
+  if (age >= viabilityYears) return SeedViability.expired;
+  if (age >= viabilityYears - 1) return SeedViability.expiringSoon;
+  return SeedViability.fresh;
+}