Adds the Offerings module and retargets the CI/CD pipeline to Api.SlpSoftware

Implements Unit 2 "Offerings" (backend module, admin CRUD UI with
drag-and-drop reordering, public GET /api/v1/offerings endpoint) and
executes the feature's D-15 CI/CD cutover, switching the deploy
pipeline's build/publish target from SlpModularCms.Api to
SlpModularCms.Api.SlpSoftware.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FWyStNL2ZsjrS7FLd7xvvN

frontend/src/features/offerings/services/useMoveOffering.ts

@@ -0,0 +1,18 @@
+import { useMutation, useQueryClient, type UseMutationOptions } from '@tanstack/react-query';
+import { api } from '@/lib/api-client';
+import type { MoveDirection } from './types';
+
+export function useMoveOffering(
+    direction: MoveDirection,
+    options?: Pick<UseMutationOptions<void, Error, string>, 'onSuccess' | 'onError'>,
+) {
+    const queryClient = useQueryClient();
+    return useMutation<void, Error, string>({
+        mutationFn: (id) => api.post<void>(`/api/v1/offerings/admin/${id}/move-${direction}`),
+        onSuccess: (data, variables, ...rest) => {
+            queryClient.invalidateQueries({ queryKey: ['offerings', 'admin'] });
+            options?.onSuccess?.(data, variables, ...rest);
+        },
+        onError: options?.onError,
+    });
+}