#339/Fix: bad request bug on conversations page loading; refactors scrolling logic

[AnyaVeselova]

• adds guard clauses in setMessagesForCurrentConversation function;
• removes stable functions from useEffects to prevent unnecessary calls;
• adds a guard in the subscription callback;
• refactors scrolling logic to prevent unnecessary re-renders;

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🔨 Latest commit	ca932c8858fb7fc85bafcf95f270395dbfdff96f

[AnyaVeselova]