Add script to aggregate metrics

[amrit110]

This pull request refactors the analytics snapshot API to serve pre-computed aggregates instead of calculating metrics on each request. The main changes include updating the API route and GCS utility functions to fetch a new analytics_aggregate.json file, removing server-side metric computation, and cleaning up unused types. This will improve performance and simplify the analytics service.

API and Data Flow Refactor:

• The /api/snapshot route (route.ts) now returns the pre-computed analytics aggregate from GCS, removing all on-the-fly metric calculations and enrichment.
• The GCS utility (gcs.ts) replaces getLatestSnapshot with getAnalyticsAggregate, fetching the new analytics_aggregate.json file. All snapshot history and bucket-checking functions are removed as they're no longer needed.

Workflow and Data Generation:

• The GitHub Actions workflow (collect-coder-analytics.yml) adds a step to run the analytics aggregation script after data collection, ensuring the aggregate is always up to date.

Codebase Cleanup:

• Unused types and interfaces related to the old snapshot structure are removed from types.ts, reflecting the switch to the new aggregate format.
• Imports and type references are updated throughout to use the new AnalyticsSnapshot type.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.84%. Comparing base (ee98df0) to head (1131db3).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #68   +/-   ##
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  Coverage   89.84%   89.84%           
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  Files          10       10           
  Lines        1438     1438           
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  Hits         1292     1292           
  Misses        146      146           

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