Add preset aggregation interval API inspired by shinyorg/Health

[Copilot]

This issue asked us to evaluate shinyorg/Health and bring over practical concepts where they improve this library.
This PR adopts its interval preset idea for bucketed queries while preserving existing TimeSpan-based APIs.

• What changed

  • Added HealthAggregationInterval enum (Minute, Hour, Day) as first-class presets for aggregate bucketing.
  • Added HealthAggregationIntervalExtensions.ToTimeSpan() to map presets to canonical TimeSpan values.
  • Added a new IHealthService overload:
    • GetAggregatedHealthDataByInterval<TDto>(HealthTimeRange, HealthAggregationInterval, CancellationToken)
  • Implemented overload in HealthService by delegating to the existing TimeSpan overload (no platform logic duplication).

• API ergonomics

  • Keeps current behavior and signatures intact.
  • Adds a clearer path for common interval use cases without requiring callers to manually construct TimeSpan.

• Documentation

  • Updated README aggregation-by-interval usage with the new preset overload.

• Example

  var hourly = await _healthService.GetAggregatedHealthDataByInterval<StepsDto>(
      weekRange,
      HealthAggregationInterval.Hour);

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/shinyorg/Health/contents
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)