Update vite off of v6.x stream once node 24 is default

For reference:

_Originally posted by @Steve-Mcl in https://github.com/FlowFuse/flowfuse/issues/7767#issuecomment-5398589821_

> **vite held at 6.4.3 (not 7/8).** vite ≥7 requires `node ^20.19 || >=22.12`, which would break our `engines: node >=20.10.0` on the dev/test toolchain. 6.4.3 is the patched release that stays compatible. It's pinned as a blanket override rather than a range-keyed one because vite is a _peer_ dependency of `@vitejs/plugin-vue` and `vitest`; a range-keyed override there trips an `ERESOLVE` peer conflict, whereas an exact pin keeps every vite edge in agreement. NOTE the peer dep supports v4, v5, v6, v7 and v8 so a blanket override is not an issue here.

With the move to Node 24 in FF 3.0 we need to address this - lets get this merged for the time being & I'll raise an issue

Inspect the package manifest for the Node engine requirement and the exact Vite override, then review the Vite, @vitejs/plugin-vue, and vitest dependency relationships. Run the dependency installation and development/test toolchain under Node 24. Done means Vite is no longer held to the 6.4.3 pin without introducing peer-resolution or compatibility failures.

Written by the indexing model from the issue text.