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

aidlc-docs/features/slpsoftware-api/inception/application-design/unit-of-work-dependency.md

@@ -10,13 +10,14 @@
 ## Sequencing
 
 ```mermaid
+%%{init: {'themeVariables': {'primaryTextColor':'#000000','textColor':'#000000','tertiaryTextColor':'#000000'}}}%%
 graph LR
     U1["Unit 1: SlpSoftware Client Setup<br/>(FR-1, FR-2, FR-3)"]
     U2["Unit 2: Offerings<br/>(FR-4..FR-8, US-01..US-12)"]
     U1 -->|"Api.SlpSoftware project must exist first"| U2
 
-    classDef foundation fill:#63b3ed,stroke:#2b6cb0,stroke-width:1px,color:#000;
-    classDef feature fill:#f6e05e,stroke:#c05621,stroke-width:1px,color:#000;
+    classDef foundation fill:#bee3f8,stroke:#2b6cb0,stroke-width:2px,color:#000000,font-weight:bold;
+    classDef feature fill:#fefcbf,stroke:#c05621,stroke-width:2px,color:#000000,font-weight:bold;
 
     class U1 foundation;
     class U2 feature;