When the RHDH dark theme is enabled, the CPU utilization and Memory utilization chart axis labels, tick marks, and legend text are rendered in black (fill: rgb(0,0,0)) against the dark background, making them nearly invisible.

Steps to Reproduce:
1. Log into RHDH
2. Navigate to Settings > Appearance > Theme and select "Dark"
3. Navigate to Cost Management > Optimizations
4. Click on any container to view the detail page with CPU and Memory utilization charts
5. Observe the chart axis labels and legend text

Expected Result:
Chart axis labels (time values on X-axis, numeric values on Y-axis) and legend text should render in a light color (white or light gray) that is readable against the dark background.

Actual Result:

• SVG text elements for axis ticks have computed fill: rgb(0,0,0) (black)
• No explicit fill attribute is set on SVG <text> elements
• The CSS color property is set to white but SVG text rendering uses fill, not color
• Affects both CPU utilization and Memory utilization charts
• Legend text ("Recommended request", "Recommended limit", "Actual usage") is also black

Root Cause:
The chart library (PatternFly Charts / Victory) does not adapt its SVG text fill colors when the Backstage dark theme is activated. The default SVG fill of black is inherited.

Environment:

• RHDH 1.9.0 (Backstage 1.45.3)
• OCP Edge 73
• Plugin: red-hat-developer-hub.plugin-redhat-resource-optimization

Note: All other dark theme elements (headings, table text, sidebar, config sections) render correctly. Only the chart SVG text is affected.