feat: implement hybrid database architecture and frontend encryption

- Add PostgreSQL + SQLite hybrid database support with automatic switching
- Implement frontend AES-GCM + RSA-OAEP encryption for sensitive data
- Add comprehensive DatabaseInterface with all required methods
- Fix compilation issues with interface consistency
- Update all database method signatures to use DatabaseInterface
- Add missing UpdateTraderInitialBalance method to PostgreSQL implementation
- Integrate RSA public key distribution via /api/config endpoint
- Add frontend crypto service with proper error handling
- Support graceful degradation between encrypted and plaintext transmission
- Add directory creation for RSA keys and PEM parsing fixes
- Test both SQLite and PostgreSQL modes successfully
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: tinkle-community <tinklefund@gmail.com>

config/database_pg.go

@@ -464,6 +464,12 @@ func (d *PostgreSQLDatabase) UpdateTraderCustomPrompt(userID, id string, customP
 	return err
 }
 
+// UpdateTraderInitialBalance 更新交易员初始余额（用于自动同步交易所实际余额）
+func (d *PostgreSQLDatabase) UpdateTraderInitialBalance(userID, id string, newBalance float64) error {
+	_, err := d.db.Exec(`UPDATE traders SET initial_balance = $1, updated_at = CURRENT_TIMESTAMP WHERE id = $2 AND user_id = $3`, newBalance, id, userID)
+	return err
+}
+
 // DeleteTrader 删除交易员
 func (d *PostgreSQLDatabase) DeleteTrader(userID, id string) error {
 	_, err := d.db.Exec(`DELETE FROM traders WHERE id = $1 AND user_id = $2`, id, userID)