Dashboard chart visual parity with Lite

[erikdarlingdata]

Problem

The Lite dashboard charts look significantly better than the full Dashboard charts:

• Marker dots: Lite uses MarkerSize=5 consistently on all data points, giving clear visual indicators. Dashboard has many MarkerSize=0 (invisible dots) and inconsistent sizes (3, 4, 5).
• Colors: Lite uses soft Material Design colors (#4FC3F7) that look great on dark backgrounds. Dashboard uses harsh stock ScottPlot colors (ScottPlot.Colors.Blue, .Red, etc.) and scattered inline color arrays.
• Consistency: Lite has one unified look across all charts. Dashboard varies between chart tabs.

Solution

1. Add a centralized 12-color Material Design 300-level palette to TabHelpers.cs
2. Replace all MarkerSize = 0/3/4 with MarkerSize = 5 across Dashboard chart files
3. Replace all stock ScottPlot colors and inline color arrays with the centralized palette
4. Preserve special markers (deadlock dots, "No data" text colors)

Files

• Dashboard/Helpers/TabHelpers.cs — new ChartColors array
• Dashboard/Controls/ResourceMetricsContent.xaml.cs
• Dashboard/Controls/SystemEventsContent.xaml.cs
• Dashboard/Controls/MemoryContent.xaml.cs
• Dashboard/Controls/QueryPerformanceContent.xaml.cs

[erikdarlingdata]

Fixed in PR #19 — centralized Material Design 300 color palette, MarkerSize standardization, status color desaturation, DataGrid spacing, and Grafana-inspired dark theme polish.