fix: add missing postgres implementations for get_portfolio_by_name_and_user and insert_ledger_trade

- add get_portfolio_by_name_and_user to PortfolioRepository protocol and
  PostgresPortfolioRepository; resolves AttributeError on all CLI name+user
  resolution paths (REQ-017)
- add insert_ledger_trade to PortfolioRepository protocol and
  PostgresPortfolioRepository; resolves HTTP 500 on POST
  /v1/assets/{asset_id}/ledger/trades (REQ-008)
- add _row_to_ledger_trade static helper; uses INSERT ... ON CONFLICT DO
  NOTHING RETURNING to return (LedgerTrade, created: bool)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/repositories/postgres.py

@@ -1169,6 +1169,73 @@ class PostgresPortfolioRepository:
             rows = cur.fetchall()
         return [self._row_to_ledger_entry(row) for row in rows]
 
+    def insert_ledger_trade(
+        self,
+        *,
+        asset_id: str,
+        order_id: str,
+        execution_id: str,
+        side: str,
+        quantity: float,
+        price: float,
+        executed_at,
+        fee_amount: float = 0.0,
+        tax_amount: float = 0.0,
+    ) -> tuple:
+        self.ensure_schema()
+        with self._connect().cursor() as cur:
+            cur.execute(
+                """
+                INSERT INTO ledger_trades
+                    (asset_id, order_id, execution_id, side, quantity, price,
+                     fee_amount, tax_amount, executed_at)
+                VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s)
+                ON CONFLICT ON CONSTRAINT uq_ledger_trades_idempotency DO NOTHING
+                RETURNING
+                    ledger_entry_id, asset_id, order_id, execution_id, side,
+                    quantity::float8, price::float8,
+                    fee_amount::float8, tax_amount::float8,
+                    executed_at, recorded_at
+                """,
+                (asset_id, order_id, execution_id, side, quantity, price,
+                 fee_amount, tax_amount, executed_at),
+            )
+            row = cur.fetchone()
+            if row is not None:
+                return self._row_to_ledger_trade(row), True
+            # Conflict: fetch existing record
+            cur.execute(
+                """
+                SELECT
+                    ledger_entry_id, asset_id, order_id, execution_id, side,
+                    quantity::float8, price::float8,
+                    fee_amount::float8, tax_amount::float8,
+                    executed_at, recorded_at
+                FROM ledger_trades
+                WHERE asset_id = %s AND order_id = %s AND execution_id = %s
+                """,
+                (asset_id, order_id, execution_id),
+            )
+            row = cur.fetchone()
+        return self._row_to_ledger_trade(row), False
+
+    @staticmethod
+    def _row_to_ledger_trade(row) -> "LedgerTrade":
+        from app.domain.models import LedgerTrade
+        return LedgerTrade(
+            ledger_entry_id=row[0],
+            asset_id=row[1],
+            order_id=row[2],
+            execution_id=row[3],
+            side=row[4],
+            quantity=float(row[5]),
+            price=float(row[6]),
+            fee_amount=float(row[7]),
+            tax_amount=float(row[8]),
+            executed_at=row[9],
+            recorded_at=row[10],
+        )
+
     def reset(self, portfolio_id: str) -> Portfolio:
         self.ensure_schema()
         with self._connect().cursor() as cur: