API Reference & Health Score Chart Improvements

New Features

Adds an interactive API reference page to the Insights public API docs site, powered by the live OpenAPI specification, and introduces an endpoint lifecycle guide covering alpha and stable versioning.

Updates Health Score Coverage category widgets to display three independent progress rings — one per scoring category — replacing a donut chart that implied percentages should sum to 100.
Fixes the signal-scores heatmap to show a full percentile-band distribution rather than just two data points per signal, giving a more accurate view of where top repositories pull ahead.
Corrects bar coloring in the Signal Availability chart, using brand blue for Linux Foundation projects and violet for others, consistent with the rest of the report.
Resolves server errors on organization pages and other endpoints, and improves error logging for health score badge requests.