fix: Add dimension fallback for table charts

[sentry]

This PR addresses issue DALGO-BACKEND-25E, a ValueError: At least one dimension is required for table charts.

Root Cause:
The normalize_dimensions function in ddpui/core/charts/charts_service.py for chart_type="table" only checked the payload.dimensions list. It did not include a fallback to payload.dimension_col or payload.extra_dimension when payload.dimensions was empty or None. This meant that table charts created using older API fields (which populate dimension_col instead of the dimensions array) would result in an empty dimension list, triggering the ValueError at line 387.

Changes Made:
Modified the normalize_dimensions function to include the fallback logic for payload.dimension_col and payload.extra_dimension within the chart_type="table" branch. Now, if payload.dimensions is empty, the function will correctly check and use the values from payload.dimension_col and payload.extra_dimension if they are present.

This change restores backward compatibility for table charts using legacy dimension fields.

Fixes DALGO-BACKEND-25E