feat(tickets): assignation de sprint en masse via multi-sélection

Permet de sélectionner plusieurs tickets dans TicketsPanel et de leur
assigner un sprint en une seule action, au lieu d'un ticket à la fois.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/features/tickets/TicketsPanel.tsx

@@ -74,6 +74,8 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
   const [showSprintPicker, setShowSprintPicker] = useState(false);
   const [selectedRefs, setSelectedRefs] = useState<Set<string>>(() => new Set());
   const [bulkStatus, setBulkStatus] = useState<TicketStatus | "">("");
+  const [showBulkSprintPicker, setShowBulkSprintPicker] = useState(false);
+  const [bulkNotice, setBulkNotice] = useState<string | null>(null);
   const [confirmBulkDelete, setConfirmBulkDelete] = useState(false);
 
   const items = vm.list?.items ?? [];
@@ -126,6 +128,7 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
   }
 
   function toggleTicketSelection(ref: string, selected: boolean) {
+    setBulkNotice(null);
     setSelectedRefs((prev) => {
       const next = new Set(prev);
       if (selected) next.add(ref);
@@ -135,6 +138,7 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
   }
 
   async function applyBulkStatus(nextStatus: TicketStatus | "") {
+    setBulkNotice(null);
     setBulkStatus(nextStatus);
     if (!nextStatus || selectedVisibleRefs.length === 0) return;
     const result = await vm.bulkUpdateStatus(selectedVisibleRefs, nextStatus);
@@ -144,7 +148,26 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
     setBulkStatus("");
   }
 
+  async function applyBulkSprint(sprint: Sprint | null) {
+    setBulkNotice(null);
+    const refs = selectedVisibleRefs;
+    if (refs.length === 0) return;
+    const result = await vm.bulkAssignSprint(refs, sprint?.id ?? null);
+    if (!result) return;
+    const failed = new Set(result.items.filter((i) => !i.ok).map((i) => i.ref));
+    const successCount = result.items.length - failed.size;
+    setSelectedRefs(new Set(refs.filter((ref) => failed.has(ref))));
+    setBulkNotice(
+      failed.size === 0
+        ? `Sprint mis à jour pour ${successCount} ticket${
+            successCount > 1 ? "s" : ""
+          }.`
+        : `Sprint mis à jour pour ${successCount}/${result.items.length} tickets. Les échecs restent sélectionnés.`,
+    );
+  }
+
   async function applyBulkDelete() {
+    setBulkNotice(null);
     const result = await vm.bulkDelete(selectedVisibleRefs);
     if (!result) return;
     const failed = new Set(result.items.filter((i) => !i.ok).map((i) => i.ref));
@@ -214,6 +237,14 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
             ]}
             onChange={(next) => void applyBulkStatus(next as TicketStatus | "")}
           />
+          <Button
+            size="sm"
+            variant="secondary"
+            disabled={vm.busy}
+            onClick={() => setShowBulkSprintPicker(true)}
+          >
+            Sprint
+          </Button>
           <Button
             size="sm"
             variant="danger"
@@ -233,6 +264,15 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
         </div>
       )}
 
+      {bulkNotice && (
+        <p
+          role="status"
+          className="mb-3 rounded-md border border-border bg-raised/60 px-3 py-2 text-sm text-content"
+        >
+          {bulkNotice}
+        </p>
+      )}
+
       {showCreate && (
         <form
           onSubmit={submitCreate}
@@ -419,6 +459,17 @@ export function TicketsPanel({ projectId, onOpen }: TicketsPanelProps) {
         onClose={() => setShowSprintPicker(false)}
       />
 
+      <SprintPicker
+        open={showBulkSprintPicker}
+        projectId={projectId}
+        selectedSprintId={null}
+        title={`Sprint pour ${selectedVisibleRefs.length} ticket${
+          selectedVisibleRefs.length > 1 ? "s" : ""
+        }`}
+        onSelect={(sprint) => void applyBulkSprint(sprint)}
+        onClose={() => setShowBulkSprintPicker(false)}
+      />
+
       {confirmBulkDelete && (
         <div
           role="dialog"