optimize dashboard collection stats query

[JULJERYT]

What does this PR do?

optimizes the dashboard statistics by reducing the number of database queries. it replaces three separate count calls with a single getStats query using conditional aggregation (sum(case when...)). this fixes a 3N query bottleneck and improves dashboard load times.

Type of change

• Performance improvement

Checklist

• I have read CONTRIBUTING.md
• pnpm typecheck passes
• pnpm --silent lint:json | jq '.diagnostics | length' returns 0
• pnpm test passes (or targeted tests for my change)
• pnpm format has been run
• I have added a changeset (if this PR changes a published package)

AI-generated code disclosure

• This PR includes AI-generated code

[changeset-bot]

🦋 Changeset detected

Latest commit: d08fc2c

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 9 packages

Name	Type
emdash	Patch
@emdash-cms/cloudflare	Patch
@emdash-cms/plugin-ai-moderation	Patch
@emdash-cms/plugin-atproto	Patch
@emdash-cms/plugin-audit-log	Patch
@emdash-cms/plugin-color	Patch
@emdash-cms/plugin-embeds	Patch
@emdash-cms/plugin-forms	Patch
@emdash-cms/plugin-webhook-notifier	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

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@emdash-cms/admin

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@emdash-cms/auth

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@emdash-cms/blocks

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emdash

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create-emdash

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@emdash-cms/plugin-ai-moderation

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@emdash-cms/plugin-atproto

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@emdash-cms/plugin-audit-log

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@emdash-cms/plugin-color

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@emdash-cms/plugin-embeds

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@emdash-cms/plugin-forms

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@emdash-cms/plugin-webhook-notifier

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commit: d08fc2c

[ascorbic]

Great, thanks!