feat(inventory): edit and delete existing lots

Lots could only be created; now they can be edited and removed:
- Repository: updateLot (LWW) + softDeleteLot (tombstone).
- Cubit: updateLot / deleteLot.
- The add-lot sheet is now a shared add/edit sheet — tapping a lot opens it
  prefilled (type, year, quantity), with a trash action to delete. The reactive
  detail view refreshes on save/delete.

Tests: repo updateLot/softDeleteLot + widget edit-lot and delete-lot. 42 green.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -32,6 +32,7 @@
     "names": "Also known as",
     "notes": "Notes",
     "addLot": "Add lot",
+    "editLot": "Edit lot",
     "deleteConfirm": "Delete this seed?",
     "year": "Year {year}",
     "noYear": "Year unknown"