fix(clip): a clip refusal speaks the user's language, and a choice in the clip form no longer sends it

The backend refuses a clip with a structured reason, but the client showed every one as the generic
"couldn't make the clip": each reason now has its own message in both languages, held to the
backend's reasons in both directions by the contract test. A segmented toggle's and the priority
stepper's buttons had no type, so inside a form one of them submitted it.

frontend/src/components/ui/PriorityStepper.tsx

@@ -36,6 +36,7 @@ function PriorityStepButton({
 }) {
   return (
     <button
+      type="button"
       onPointerDown={(e) => {
         // Keep receiving pointer events even if the pointer drifts off the small button mid-hold.
         try {
@@ -162,6 +163,7 @@ export function PriorityStepper({
           } ${cls.value}`}
         >
           <button
+            type="button"
             ref={editTarget}
             onClick={beginEdit}
             aria-label={t("common.priority.edit")}

frontend/src/components/ui/SegmentedToggle.tsx

@@ -62,6 +62,8 @@ export default function SegmentedToggle<T extends string>({
       {options.map((o) => (
         <button
           key={o.value}
+          // A choice, never a submit: inside a form (the clip panel) a bare button would send it.
+          type="button"
           onClick={() => onChange(o.value)}
           title={o.title}
           aria-pressed={value === o.value}