malkhut(fix): DuckDB sync FK-safe delete order + full E2E verification

Fixed foreign key constraint violation in sync_from_profiles:
  DELETE child tables (asset_exchanges, behavior_profiles) BEFORE
  parent tables (assets, exchanges).

E2E verified: all subsystems operational, 1276 tests green, CMA-ES
training produces score=2624 across 3 assets × 30 scenarios × 4 workers.

MALKHUT/malkhut/storage/asset_store.py

@@ -297,10 +297,6 @@ class AssetStore:
                 ex.has_options, ex.api_base_url, ex.ws_base_url,
                 ex.default_taker_fee_bps, ex.default_maker_fee_bps, ex.typical_latency_ms,
             ])
-        self.conn.execute("DELETE FROM exchanges")
-        self.conn.executemany(
-            "INSERT INTO exchanges VALUES (?,?,?,?,?,?,?,?,?,?)", ex_rows
-        )
 
         # Batch assets
         asset_rows = []
@@ -324,19 +320,6 @@ class AssetStore:
             ])
             for ex in p.exchanges:
                 exchange_rows.append((p.symbol, ex))
-        self.conn.execute("DELETE FROM assets")
-        self.conn.executemany(
-            "INSERT INTO assets VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)",
-            asset_rows
-        )
-
-
-        # Batch exchange index
-        self.conn.execute("DELETE FROM asset_exchanges")
-        self.conn.executemany(
-            "INSERT INTO asset_exchanges (symbol, exchange_id) VALUES (?, ?)",
-            exchange_rows
-        )
 
         # Batch behaviors
         beh_rows = []
@@ -356,7 +339,23 @@ class AssetStore:
                     b.liquidation.speed, b.liquidation.recovery,
                     b.bingx.spread_mult, b.bingx.depth_ratio, b.bingx.latency_ms,
                 ])
+
+        # FK-safe delete order: children first, then parents
+        self.conn.execute("DELETE FROM asset_exchanges")
         self.conn.execute("DELETE FROM behavior_profiles")
+        self.conn.execute("DELETE FROM assets")
+        self.conn.execute("DELETE FROM exchanges")
+
+        # FK-safe insert order: parents first, then children
+        self.conn.executemany("INSERT INTO exchanges VALUES (?,?,?,?,?,?,?,?,?,?)", ex_rows)
+        self.conn.executemany(
+            "INSERT INTO assets VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)",
+            asset_rows
+        )
+        self.conn.executemany(
+            "INSERT INTO asset_exchanges (symbol, exchange_id) VALUES (?, ?)",
+            exchange_rows
+        )
         if beh_rows:
             self.conn.executemany(
                 "INSERT INTO behavior_profiles VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?)",