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/components/layout/Sidebar.tsx

@@ -1,6 +1,6 @@
 import { Link } from '@tanstack/react-router';
 import { useTranslation } from 'react-i18next';
-import { LayoutDashboard, Users, FileText, Settings, X } from 'lucide-react';
+import { LayoutDashboard, Users, FileText, Package, Settings, X } from 'lucide-react';
 import type { LucideIcon } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import { useAuth } from '@/features/auth/context/auth-context';
@@ -27,6 +27,14 @@ const NAV_ITEMS: NavItem[] = [
     { to: '/dashboard', labelKey: 'nav.dashboard', icon: LayoutDashboard, testId: 'nav-dashboard' },
     { to: '/users', labelKey: 'nav.users', icon: Users, testId: 'nav-users', roles: ['Owner', 'Administrator'] },
     { to: '/cms', labelKey: 'nav.cms', icon: FileText, testId: 'nav-cms', roles: ['Owner'], requiredModule: 'Master' },
+    {
+        to: '/offerings',
+        labelKey: 'nav.offerings',
+        icon: Package,
+        testId: 'nav-offerings',
+        roles: ['Owner', 'Administrator'],
+        requiredModule: 'Offerings',
+    },
 ];
 
 const SETTINGS_ITEM: NavItem = {