fix(svelte-db): initialize useLiveQuery data synchronously for SSR

[elohmeier]

🎯 Changes

$effect doesn't run during server-side rendering, so internalData and state remained empty even when the collection was populated with initial data via sync config.

This adds synchronous initialization of state and internalData from the collection immediately after $state declarations, ensuring data is available for SSR before effects run on the client.

Changes:

• Add synchronous initialization block in useLiveQuery.svelte.ts
• Add unit tests to verify SSR behavior (data available before flushSync)

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

[changeset-bot]

🦋 Changeset detected

Latest commit: 21dfb4b

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

This PR includes changesets to release 1 package

Name	Type
@tanstack/svelte-db	Patch

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commit: 21dfb4b