Fix candles sync for currency converter

[ZIMkaRU]

This PR fixes the candles sync for the currency converter

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To convert the first ledgers to USD it needs to provide some overlap of candles:

• the first entries in the ledgers with their timestamps may not have corresponding entries in the candles
• in rare cases, this may result in missing several entries when converting to USD
• the idea is to provide a 5 day overlap of candles in relation to the first entries in the ledgers
• the ability to convert balances into USD is also added for already synchronized but not converted records (for ordinary users and sub-accounts)

[ezewer]

Looks good to me!