feat(api): add /api/admin/requests approval queue

Three admin-gated handlers: GET /admin/requests (list by status),
POST /admin/requests/:id/approve (with optional overrides), and
POST /admin/requests/:id/reject. testHandlers updated to inject a
real clientFn so Approve exercises Lidarr in integration tests.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/api/api.go

@@ -68,6 +68,9 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 				admin.Post("/lidarr/test", h.handleTestLidarrConnection)
 				admin.Get("/lidarr/quality-profiles", h.handleListQualityProfiles)
 				admin.Get("/lidarr/root-folders", h.handleListRootFolders)
+				admin.Get("/requests", h.handleListAdminRequests)
+				admin.Post("/requests/{id}/approve", h.handleApproveRequest)
+				admin.Post("/requests/{id}/reject", h.handleRejectRequest)
 			})
 		})
 	})