feat(ECR-044): RhythmConfig 写面闭环并 Closed

复用 admin.explore.write、POST/PUT+审计、C端 GET /rhythm/configs、
H5 无 active 空态/失败回退；migration 000053。ExploreConfig Loop STOP，禁自动 ECR-045。

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

docs/CONTRACT_DIFF/ECR-044.yaml

@@ -0,0 +1,20 @@
+ecr: ECR-044
+capability: ExploreConfig
+change:
+  type: additive
+breaking_change: false
+migration_required: true
+apis:
+  - method: POST
+    path: /api/v1/admin/explore/rhythm-configs
+    change: added
+  - method: PUT
+    path: /api/v1/admin/explore/rhythm-configs/{id}
+    change: added
+  - method: GET
+    path: /api/v1/rhythm/configs
+    change: added
+perms:
+  - code: admin.explore.write
+    change: reused
+migration: 000053_ops_rhythm_config_write