feat(admin): send daily coding plan inventory to Slack

[jeanduplessis]

Summary

Send a Slack summary of Coding Plans credential inventory every day at 12:00 UTC.

Why this change is needed

Coding Plans inventory requires regular operational visibility. A daily summary makes available capacity and credentials needing revocation visible without requiring administrators to inspect the Admin UI manually.

How this is addressed

• Add a server-only Slack notification helper supporting text and Block Kit payloads.
• Build an inventory summary with total and per-plan counts, friendly plan names, revocation warnings, and a link to the Coding Plans Admin UI.
• Add an authenticated cron endpoint scheduled for 12:00 UTC every day.
• Treat a missing webhook as optional configuration: log a warning and complete the cron successfully.
• Report database, network, and Slack delivery failures as failed cron runs.
• Keep notifications independent from Admin UI inventory mutations.

Human Verification

• Confirmed the formatted Block Kit message renders successfully in Slack.

Manual Slack verification

• Sent the proposed inventory fixture through the configured incoming webhook.
• Confirmed totals, per-plan counts, revocation warnings, and snapshot time render correctly.
• Replaced the interactive button with a normal Slack link so the message does not require a Slack interactivity URL.

Reviewer Notes

Human Reviewer Flags

• The report runs as an independent Vercel cron at 0 12 * * *; inventory mutations do not trigger notifications.
• Missing webhook configuration is intentionally non-fatal. Other delivery failures remain fatal so Vercel and Sentry expose unhealthy runs.
• The webhook must be configured as the server-only SLACK_ADMIN_NOTIFICATIONS_WEBHOOK_URL secret before deployment.

Code Reviewer Agent

Code Reviewer Notes

• The cron endpoint uses the existing constant-time CRON_SECRET authorization helper.
• Slack fetch errors are replaced with sanitized errors because native fetch errors may contain the secret webhook URL.
• The fallback text field remains available to notifications and assistive clients that do not render Block Kit.
• Unknown inventory statuses are displayed instead of being silently discarded.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Reviewed the new Slack admin-notification helper, Coding Plans inventory formatter, authenticated daily cron route, env plumbing, and tests; no security, correctness, or reliability defects found in the changed lines (high confidence).

Verification Notes

• Webhook secret handling: fetch errors are replaced with AdminSlackNotificationError, so the webhook URL cannot leak into logs or Sentry; the response body is drained before the status check.
• Cron authorization uses the existing constant-time isCronAuthorizationValid helper with the same module-level CRON_SECRET guard as api/cron/coding-plans-billing.
• getEnvVariable returns '' when unset, so the missing-webhook branch in sendAdminSlackNotification is reached correctly and the cron still succeeds, matching the documented intent.
• Inventory math checked against getKeyInventoryCounts: loaded sums all statuses, consistent with the Admin UI totalCredentialCount; unknown statuses are surfaced rather than dropped.
• Slack mrkdwn escaping is applied to block content; unescaped plan names only reach the fallback text, and plan_id/provider_id are catalog-validated in uploadKeysToInventory, so no mrkdwn/link injection path exists.
• formatSnapshotTime produces YYYY-MM-DD HH:MM UTC for all toISOString() output; Block Kit block/field counts stay well within Slack limits for the current 3-plan catalog.
• Env var registered in the three expected places (config.server.ts, .env.local.example, ENVIRONMENT.md) and the cron is wired in apps/web/vercel.json at 0 12 * * *.
• No .md image markup and no landing-page/SEO surface in this diff, so those custom rules do not apply. No new listeners, timers, or unbounded caches were introduced, so no memory-leak risk.

Files Reviewed (10 files)

• apps/web/src/app/api/cron/coding-plans-inventory-summary/route.ts
• apps/web/src/app/api/cron/coding-plans-inventory-summary/route.test.ts
• apps/web/src/lib/coding-plans/inventory-slack-summary.ts
• apps/web/src/lib/coding-plans/inventory-slack-summary.test.ts
• apps/web/src/lib/slack/admin-notifications.ts
• apps/web/src/lib/slack/admin-notifications.test.ts
• apps/web/src/lib/config.server.ts
• apps/web/vercel.json
• .env.local.example
• ENVIRONMENT.md

Assumptions

• Tests were not executed (read-only review); assertions were verified by reading the code paths they exercise.
• SLACK_ADMIN_NOTIFICATIONS_WEBHOOK_URL is assumed to be configured in Vercel before deploy, as stated in the PR description.

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_{Reviewed by claude-opus-5 · Input: 52 · Output: 18.5K · Cached: 1.7M}

_{Review guidance: REVIEW.md from base branch main}