feat(sprints): interface de création et gestion des sprints (frontend)

Ticket #11 — surface UI de gestion des sprints (frontend pur).

- Nouveau composant SprintManager : création (nom optionnel), édition et
  gestion du cycle de vie d'un sprint, contrôles accessibles (pas de DnD).
- useTickets étendu aux opérations de gestion de sprint ; ports, adaptateurs
  (ticket.ts, mock/index.ts) et TicketsPanel câblés en conséquence.
- Tests Vitest associés (tickets.test.tsx).

Typecheck / vitest (497+ tests) / build verts.

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

frontend/src/adapters/mock/index.ts

@@ -1815,6 +1815,7 @@ export class MockTicketGateway implements TicketGateway {
   private carnets = new Map<string, Map<string, string>>();
   private counters = new Map<string, number>();
   private sprints = new Map<string, Map<string, Sprint>>();
+  private sprintCounters = new Map<string, number>();
 
   constructor(private readonly system?: MockSystemGateway) {}
 
@@ -2141,6 +2142,118 @@ export class MockTicketGateway implements TicketGateway {
     });
     return structuredClone(ticket);
   }
+
+  async createSprint(projectId: string, name: string): Promise<Sprint> {
+    const sprints = this.projectSprints(projectId);
+    const seq = (this.sprintCounters.get(projectId) ?? 0) + 1;
+    this.sprintCounters.set(projectId, seq);
+    const order =
+      sprints.size === 0
+        ? 1
+        : Math.max(...[...sprints.values()].map((s) => s.order)) + 1;
+    const sprint: Sprint = {
+      id: `mock-sprint-${projectId}-${seq}`,
+      order,
+      name,
+      status: "planned",
+      ticketCount: 0,
+      version: 1,
+    };
+    sprints.set(sprint.id, sprint);
+    this.system?.emit({
+      type: "sprintCreated",
+      sprintId: sprint.id,
+      order: sprint.order,
+    });
+    return structuredClone(sprint);
+  }
+
+  async renameSprint(
+    projectId: string,
+    sprintId: string,
+    name: string,
+    expectedVersion: number,
+  ): Promise<Sprint> {
+    const sprint = this.requireSprint(projectId, sprintId);
+    this.guardSprint(sprint, expectedVersion);
+    sprint.name = name;
+    sprint.version += 1;
+    this.system?.emit({
+      type: "sprintRenamed",
+      sprintId,
+      name,
+      version: sprint.version,
+    });
+    return structuredClone(sprint);
+  }
+
+  async reorderSprints(
+    projectId: string,
+    orderedIds: string[],
+  ): Promise<Sprint[]> {
+    const sprints = this.projectSprints(projectId);
+    for (const id of orderedIds) this.requireSprint(projectId, id);
+    // Assign 1-based order following the provided id sequence; ids omitted from
+    // `orderedIds` keep their relative order after the listed ones.
+    const rest = [...sprints.values()]
+      .filter((s) => !orderedIds.includes(s.id))
+      .sort((a, b) => a.order - b.order)
+      .map((s) => s.id);
+    [...orderedIds, ...rest].forEach((id, index) => {
+      const sprint = sprints.get(id);
+      if (sprint) {
+        sprint.order = index + 1;
+        this.system?.emit({
+          type: "sprintReordered",
+          sprintId: id,
+          order: sprint.order,
+          version: sprint.version,
+        });
+      }
+    });
+    return this.listSprints(projectId);
+  }
+
+  async deleteSprint(projectId: string, sprintId: string): Promise<void> {
+    this.requireSprint(projectId, sprintId);
+    // Delete unassigns the sprint's tickets (it does NOT delete them): they fall
+    // back to the "no sprint" bucket.
+    for (const ticket of this.projectTickets(projectId).values()) {
+      if (ticket.sprintId === sprintId) {
+        ticket.sprintId = null;
+        this.bump(ticket);
+        this.system?.emit({
+          type: "issueSprintChanged",
+          issueRef: ticket.ref,
+          from: sprintId,
+          to: null,
+          version: ticket.version,
+        });
+      }
+    }
+    this.projectSprints(projectId).delete(sprintId);
+    this.system?.emit({ type: "sprintDeleted", sprintId });
+  }
+
+  private requireSprint(projectId: string, sprintId: string): Sprint {
+    const sprint = this.projectSprints(projectId).get(sprintId);
+    if (!sprint) {
+      throw {
+        code: "NOT_FOUND",
+        message: `sprint ${sprintId} not found`,
+      } as GatewayError;
+    }
+    return sprint;
+  }
+
+  private guardSprint(sprint: Sprint, expectedVersion: number): void {
+    if (sprint.version !== expectedVersion) {
+      throw {
+        code: "INVALID",
+        message: `sprint version conflict: expected ${expectedVersion}, actual ${sprint.version}`,
+      } as GatewayError;
+    }
+  }
 }
 
 function mostRestrictive(