feat(tickets): ajoute les pièces jointes sur tickets (#108)

Stockage flat côté ticket + métadonnées d'attachments, lecture exposée côté
backend/MCP, et UI minimale de liste/ajout dans TicketDetail. Traverse le
domaine (Issue, ports), l'application (usecases + assistant de ticket), les
adaptateurs infra/MCP (issues store, orchestrateur), les DTO backend/web-
server/app-tauri, et le frontend (domain/ports/adapters/hooks/UI).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/features/tickets/TicketDetail.tsx

@@ -76,6 +76,18 @@ function Section({
   );
 }
 
+function formatBytes(bytes: number): string {
+  if (!Number.isFinite(bytes) || bytes <= 0) return "0 B";
+  const units = ["B", "KB", "MB", "GB"];
+  let value = bytes;
+  let unit = 0;
+  while (value >= 1024 && unit < units.length - 1) {
+    value /= 1024;
+    unit += 1;
+  }
+  return `${value.toFixed(unit === 0 ? 0 : 1)} ${units[unit]}`;
+}
+
 export function TicketDetail({
   projectId,
   ticketRef,
@@ -389,6 +401,72 @@ export function TicketDetail({
             </div>
           </Section>
 
+          {/* ── Attachments (#108) ── */}
+          <Section title="Pièces jointes">
+            <div className="flex flex-wrap items-center justify-between gap-2">
+              <p className="text-xs text-muted">
+                {t.attachments.length === 0
+                  ? "Aucune pièce jointe."
+                  : `${t.attachments.length} pièce${
+                      t.attachments.length > 1 ? "s" : ""
+                    } jointe${t.attachments.length > 1 ? "s" : ""}.`}
+              </p>
+              <Button
+                size="sm"
+                disabled={vm.busy}
+                loading={vm.busy}
+                onClick={() => void vm.attachFile()}
+              >
+                Joindre
+              </Button>
+            </div>
+            {t.attachments.length > 0 && (
+              <ul className="flex flex-col gap-2">
+                {t.attachments.map((attachment) => (
+                  <li
+                    key={attachment.id}
+                    className="flex flex-wrap items-center justify-between gap-2 rounded-md border border-border bg-raised/30 px-3 py-2"
+                  >
+                    <div className="min-w-0">
+                      <p className="truncate text-sm font-medium text-content">
+                        {attachment.filename}
+                      </p>
+                      <p className="text-xs text-muted">
+                        {formatBytes(attachment.sizeBytes)} ·{" "}
+                        {attachment.mime || "application/octet-stream"}
+                      </p>
+                    </div>
+                    <div className="flex shrink-0 items-center gap-2">
+                      <span
+                        className={cn(
+                          "rounded-full px-2 py-0.5 text-xs font-medium",
+                          attachment.summarizedInCarnet
+                            ? "bg-success/10 text-success"
+                            : "bg-raised text-muted",
+                        )}
+                      >
+                        Résumé : {attachment.summarizedInCarnet ? "oui" : "non"}
+                      </span>
+                      {!attachment.summarizedInCarnet && (
+                        <Button
+                          size="sm"
+                          variant="ghost"
+                          disabled={vm.busy}
+                          onClick={() =>
+                            void vm.markAttachmentSummarized(attachment.id)
+                          }
+                          aria-label={`marquer résumé ${attachment.filename}`}
+                        >
+                          Marquer résumé
+                        </Button>
+                      )}
+                    </div>
+                  </li>
+                ))}
+              </ul>
+            )}
+          </Section>
+
           {/* ── Links (F5) ── */}
           <Section title="Linked tickets">
             {t.links.length === 0 ? (