feat(apicore-sync): field-level ownership between ApiCore and the shop

ApiCore stays the source of truth for beekeeping facts, Wabenhain for
everything sales-related; both remain separate packages talking only over
ApiCore's HTTP API.

- Batches: lot number, fill date, best-before date and filled jar count
  now follow ApiCore on every run (before: created once, corrections never
  arrived). remainingGlasses - the shop's own stock - is never written; if
  it exceeds a corrected fill quantity, the run reports it instead of
  silently adjusting.
- Batches are matched by the new Batch.apicoreBottlingId instead of the lot
  number, so correcting a lot number in ApiCore no longer creates a second
  batch. Existing synced batches are adopted once via their lot number.
- Harvests: date and year always follow ApiCore, also when published or
  edited; type, location and text stay as maintained in the admin.
- Products stay entirely shop-owned after creation (weight drives the
  legally required unit price, so it is never changed automatically).
- Admin panel: batch update count and stock-conflict notice; intro text
  states which system owns which fields.

Migration is additive (nullable unique column).

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

src/i18n/dictionaries/en.ts

@@ -1131,12 +1131,12 @@ export const en: Dictionary = {
   adminApiCoreSync: {
     heading: "ApiCore sync",
     intro:
-      "Fetches harvests, batches and products from ApiCore in one run — in that order, because each step builds on the previous one. Harvests and products are created as drafts: harvests unpublished, products inactive and without a price, because ApiCore does not hold sales prices. Each bottling run becomes its own vintage. Entries already released or edited in the admin are never overwritten; internal ApiCore notes are not copied.",
+      "Fetches harvests, batches and products from ApiCore in one run — in that order, because each step builds on the previous one. Harvests and products are created as drafts: harvests unpublished, products inactive and without a price, because ApiCore does not hold sales prices. Each bottling run becomes its own vintage. Beekeeping facts (dates, lot number, best-before date, filled quantity) always come from ApiCore; texts, prices, images, visibility and shop stock stay as maintained here. Internal ApiCore notes are not copied.",
     button: "Sync everything",
     resultHarvests: (created, updated, skipped, failed) =>
       `Harvests: ${created} created, ${updated} updated, ${skipped} skipped${failed > 0 ? `, ${failed} failed` : ""}.`,
-    resultBatches: (created, skipped, failed) =>
-      `Batches: ${created} created, ${skipped} skipped${failed > 0 ? `, ${failed} failed (see server log)` : ""}.`,
+    resultBatches: (created, updated, skipped, failed) =>
+      `Batches: ${created} created, ${updated} updated, ${skipped} unchanged${failed > 0 ? `, ${failed} failed (see server log)` : ""}.`,
     resultProducts: (created, skipped, failed) =>
       `Products: ${created} new vintage${created === 1 ? "" : "s"}, ${skipped} skipped${failed > 0 ? `, ${failed} failed (see server log)` : ""}.`,
     pending: (count) =>
@@ -1144,7 +1144,9 @@ export const en: Dictionary = {
     discontinued: (count) =>
       `${count} bottling run${count === 1 ? "" : "s"} belong to an article ApiCore no longer carries, so no new vintage was created. Existing ones stay on sale.`,
     protectedDrafts: (count) =>
-      `${count} harvest draft${count === 1 ? " was" : "s were"} already edited in the admin and therefore not overwritten.`,
+      `${count} harvest draft${count === 1 ? " was" : "s were"} already edited in the admin: type, location and text stay, only date and year come from ApiCore.`,
+    stockConflicts: (count) =>
+      `For ${count} batch${count === 1 ? "" : "es"} the shop stock exceeds the quantity filled according to ApiCore. Please check the stock under batches — it was not changed automatically.`,
     lastRun: (when) => `Last complete run: ${when}`,
     neverRun: "No complete run yet.",
     error: "Sync with ApiCore failed.",