feat(tickets): tri de la liste de tickets côté backend (#21)

Ajoute le paramètre de tri dans TicketListQuery et l'expose via
ticket_list (surface app-tauri + MCP). Ports et adaptateur mock
frontend alignés sur le contrat de tri. La partie UI (contrôle de tri
dans TicketFacetsBar) suivra dans un commit frontend dédié.

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

frontend/src/ports/index.ts

@@ -713,6 +713,7 @@ export interface ConversationGateway {
  * Status and priority are **multi-select**: `statuses`/`priorities` are sets of
  * accepted values with OR semantics *within* a facet and AND *across* facets. An
  * empty or absent array means "no constraint on this facet" (all values pass).
+ * `sort` is optional; when absent, the backend preserves its historical order.
  */
 export interface TicketListQuery {
   statuses?: TicketStatus[];
@@ -720,10 +721,20 @@ export interface TicketListQuery {
   assignedAgentId?: string;
   /** Free-text match over title/description. */
   text?: string;
+  sort?: TicketListSort;
   limit?: number;
   cursor?: string;
 }
 
+export type TicketListSortField = "number" | "priority" | "status" | "title";
+
+export type TicketListSortDirection = "asc" | "desc";
+
+export interface TicketListSort {
+  field: TicketListSortField;
+  direction: TicketListSortDirection;
+}
+
 /** Input for {@link TicketGateway.create}. */
 export interface CreateTicketInput {
   title: string;