feat: garden care reminder bodies, task sync, upload cleanup

- care reminders now fire with plant-specific body ("Time to water Pothos")
  via title/body columns on the reminders table (migration 0016)
- bi-directional task sync: checking off a garden-linked task list item
  creates a care log; logging care from garden marks the linked task done
  (list_items.metadata stores gardenPlantId + gardenCareType linkage)
- upload error response no longer leaks debug detail; error message
  corrected from "5 MB" to "100 MB"

src/modules/_core/registry.ts

@@ -73,6 +73,26 @@ export function getWidgetMetas(): SerializedWidgetMeta[] {
   );
 }
 
+// ─── Item toggle hooks ────────────────────────────────────────────────────────
+
+type ItemTogglePayload = {
+  itemId: string;
+  metadata: Record<string, unknown>;
+  done: boolean;
+  userId: string;
+};
+type ItemToggleHook = (payload: ItemTogglePayload) => Promise<void>;
+
+const itemToggleHooks = new Map<string, ItemToggleHook>();
+
+export function registerItemToggleHook(id: string, hook: ItemToggleHook): void {
+  itemToggleHooks.set(id, hook);
+}
+
+export async function fireItemToggleHooks(payload: ItemTogglePayload): Promise<void> {
+  await Promise.allSettled([...itemToggleHooks.values()].map((h) => h(payload)));
+}
+
 export function getQuickAdds(): SerializedQuickAddItem[] {
   return [...modules.values()].flatMap((manifest) =>
     (manifest.quickAdds ?? []).map(({ id, label, icon, url }) => ({