feat(ECR-041): OpsCMS Banner 薄写面（Write-Wave 首刀）

Admin POST/PUT + admin.cms.write/审计；C 端 GET /home/banners；首页投影回退静态 homeFeeds；migration 000051；不碰 FeedSlot/支付/UGC。

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/CONTRACT_DIFF/ECR-041.yaml

@@ -0,0 +1,27 @@
+ecr: ECR-041
+capability: OpsCMS
+bounded_context: Ops_CMS_NoUGC
+parent: WAVE0-FROZEN
+write_wave: docs/WAVE0/WRITE_WAVE_AUTHORIZATION.md
+predecessor: ECR-024
+change:
+  type: additive
+breaking_change: false
+migration_required: true
+compatibility_notes: >
+  Banner write + C-end home banners. Forbidden: FeedSlot write / UGC / real payment / soft-delete.
+
+apis:
+  - method: POST
+    path: /api/v1/admin/cms/banners
+    change: added
+  - method: PUT
+    path: /api/v1/admin/cms/banners/{id}
+    change: added
+  - method: GET
+    path: /api/v1/home/banners
+    change: added
+perms:
+  - code: admin.cms.write
+    change: added
+migration: 000051_ops_banner_write