refactor: extract chart data processing into separate utility functions

Addresses CodeRabbit feedback by breaking down the complex chartData useMemo hook
into smaller, focused functions:
- validateInputData: Handles input validation
- detectTimeSeriesData: Detects time series data patterns
- processTimeSeriesData: Processes time series chart data
- processNumericSeriesData: Processes numeric chart data

This improves maintainability, testability, and follows Single Responsibility Principle.

Author: weinStag