feat(backend): Add org statistics endpoint with daily/weekly/monthly aggregates

[FaveTeamz]

Summary

Org maintainers have no way to view statistics about their organization's activity: how many applications were received, assignments made, or completions logged over a period. This data is essential for org governance and capacity planning.

Problem

Maintainers must manually count events from the event history to understand their org's activity trends. There is no API endpoint providing pre-aggregated statistics.

Acceptance Criteria

• Add GET /api/orgs/:org_id/stats?period=7d|30d|90d endpoint
• Response includes: total applications, total assignments, total completions, total revocations, unique contributors, avg time to assignment (hours), avg time to completion (hours)
• Time series data: daily counts for the requested period (for charting)
• Cache results for 15 minutes in Redis
• Require a valid API key associated with the org (maintainer or admin)
• Return 404 if org_id is not registered
• Document endpoint in docs/api-reference.md with example response

[A-one-tech]

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[maybay-dev]

@maybay-dev has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

please i will love to work on these issue thank you

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[Peace-001]

@Peace-001 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Good day maintainer i would like to work on this issue

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[obalogunolabimpeoluwakanyinsol-ai]

@obalogunolabimpeoluwakanyinsol-ai has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hello maintainer i will like to work on this issue

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[drips-wave]

Congratulations, @obalogunolabimpeoluwakanyinsol-ai! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

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[drips-wave]

This issue has been completed by @obalogunolabimpeoluwakanyinsol-ai as part of the Stellar Wave Program's 8th Wave 🥳

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