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

src/SlpModularCms.Api.SlpSoftware/appsettings.Development.json

@@ -34,12 +34,19 @@
     "MasterUrl": "https://localhost:7223"
   },
   "Cors": {
-    // Port 5175, not 5173: that's Api's own frontend dev port (see frontend/package.json's
-    // plain `pnpm dev`). This project is reached via `pnpm dev:slpsoftware`, which runs the
-    // frontend dev server on 5175 (see .env.slpsoftware.local / package.json).
+    // 5175: this repo's admin frontend, reached via `pnpm dev:slpsoftware` (see
+    // .env.slpsoftware.local / package.json) — NOT the same as 5173, which is Api's own
+    // (Master) admin frontend dev port and would be the wrong origin to allow here.
+    // 5173: the actual public SlpSoftware website (separate repo/workspace,
+    // K:\Development\SlpSoftware\Projects\SlpSoftware), calling the anonymous
+    // GET /api/v1/offerings endpoint from its own Vite dev server. Coincidentally the same
+    // port number as Api's admin frontend above, but a different codebase/origin entirely —
+    // both need to be allowed here since Api.SlpSoftware serves both consumers.
     "AllowedOrigins": [
       "http://localhost:5175",
-      "https://localhost:5175"
+      "https://localhost:5175",
+      "http://localhost:5173",
+      "https://localhost:5173"
     ]
   },
   "RateLimiting": {