SSR and hydration support for @tanstack/vue-db

[KyleAMathews]

Follow-up to #1623 (Phase 6). #1564 added core DbClient, collection descriptors, dehydration/hydration, and React/Svelte integrations. The current SSR guide explicitly leaves Vue client-provider work for a later change.

Goal

Support server rendering of Vue live queries with a request-scoped DbClient, then hydrate the same result into a stable browser client. Keep Vue-native reactivity and existing non-SSR useLiveQuery usage.

Acceptance criteria

• Provide an idiomatic Vue app/client scope (for example, provide/inject) so live queries can resolve collection descriptors against the correct DbClient. A fresh server client is used per request; direct collection inputs continue to work.
• A server render can preload a collection or live query, render its rows, and serialize dbClient.dehydrate() without sharing state between requests.
• The browser hydrates that state before the first live-query read, renders matching initial rows and order, and hands off to normal sync without duplicate rows or a hydration mismatch.
• Add an integration or E2E test using real Vue server render and browser hydration. Cover request isolation and a post-hydration live update.
• Document Vue setup, the supported query forms, and any remaining SSR limits (including infinite queries if they need separate work).

Use the existing core SSR payload and observer contracts; a new cross-framework payload format is outside this issue.