Add force_update_candles configuration to OKX data collector

- Introduced `force_update_candles` option in `okx_config.json` to control candle update behavior.
- Updated `OKXCollector` to handle candle storage based on the `force_update_candles` setting, allowing for either updating existing records or preserving them.
- Enhanced logging to reflect the action taken during candle storage, improving traceability.
- Updated database schema to include `updated_at` timestamp for better tracking of data changes.

database/schema_clean.sql

@@ -18,7 +18,7 @@ CREATE TABLE market_data (
     id SERIAL PRIMARY KEY,
     exchange VARCHAR(50) NOT NULL DEFAULT 'okx',
     symbol VARCHAR(20) NOT NULL,
-    timeframe VARCHAR(5) NOT NULL, -- 1m, 5m, 15m, 1h, 4h, 1d
+    timeframe VARCHAR(5) NOT NULL, -- 1s, 5s, 10s, 15s, 30s, 1m, 5m, 15m, 1h, 4h, 1d
     timestamp TIMESTAMPTZ NOT NULL,
     open DECIMAL(18,8) NOT NULL,
     high DECIMAL(18,8) NOT NULL,
@@ -27,6 +27,7 @@ CREATE TABLE market_data (
     volume DECIMAL(18,8) NOT NULL,
     trades_count INTEGER, -- number of trades in this candle
     created_at TIMESTAMPTZ DEFAULT NOW(),
+    updated_at TIMESTAMPTZ DEFAULT NOW(),
     CONSTRAINT unique_market_data UNIQUE(exchange, symbol, timeframe, timestamp)
 );