feat(web): per-mutation success/error toast metadata (#47)

Declare meta on all 18 mutation hooks: meta.successMessage (toast.* key)
on every discrete user action, meta.suppressErrorToast where the consuming
component already renders the error inline. Corrected useUpdateFieldDefinition
to suppress (FieldForm renders update.isError as form.rejected inline).

Add an RTL+MSW integration test wiring the real MutationCache via
makeQueryClient() + ToastRegion: success toast, catch-all error toast, and
suppressed-no-toast. Tidy the toast Close aria-label to t("common.close")
with en/sv parity.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/src/components/ui/toast.tsx

@@ -1,10 +1,12 @@
 import type * as React from "react";
+import { useTranslation } from "react-i18next";
 import { Toast as ToastPrimitive } from "@base-ui/react/toast";
 
 import { cn } from "@/lib/utils";
 import { toastManager } from "@/toast/toast-manager";
 
 function ToastList() {
+  const { t } = useTranslation();
   const { toasts } = ToastPrimitive.useToastManager();
   return toasts.map((toast) => (
     <ToastPrimitive.Root
@@ -31,7 +33,7 @@ function ToastList() {
       </div>
       <ToastPrimitive.Close
         data-slot="toast-close"
-        aria-label="Close"
+        aria-label={t("common.close")}
         className="text-neutral-400 hover:text-neutral-700"
       >
         ×