rebuild(stage-7): deliver ladder and sector rotation

next/backend/database/migrations/m0004_sector_members.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+import sqlite3
+
+from backend.database.migrations.runner import Migration
+
+
+def upgrade(connection: sqlite3.Connection) -> None:
+    connection.execute(
+        """
+        CREATE TABLE sector_member_snapshots (
+            trade_date TEXT NOT NULL,
+            sector_name TEXT NOT NULL,
+            sector_code TEXT NOT NULL,
+            observed_at TEXT NOT NULL,
+            source TEXT NOT NULL,
+            coverage REAL NOT NULL CHECK (coverage >= 0 AND coverage <= 1),
+            payload_json TEXT NOT NULL,
+            PRIMARY KEY (trade_date, sector_name)
+        )
+        """
+    )
+
+
+def downgrade(connection: sqlite3.Connection) -> None:
+    connection.execute("DROP TABLE sector_member_snapshots")
+
+
+MIGRATION = Migration(
+    version=4,
+    name="create_sector_member_snapshots",
+    signature="market:v2:dated-shenwan-sector-members",
+    upgrade=upgrade,
+    downgrade=downgrade,
+)