ZeroProxy Multi-user support

Probably more for [the proxy project](https://github.com/zeronetproxy/ZeroNetProxy), but users can edit the site, though not sign it, and pollute the proxy.

E.g. A user repeatedly hits the "Add post" button, (as seen on (http://zero.network:43110/1Bu6sb3PYD1XzbcqqQgVw42S6C83Yzdweb at the moment).

It DOES NOT affect the ZeroNet apart from the proxy, because it isn't signed or published.
It DOES affect anyone deciding to use that proxy.
It DOES affect everyone using this blog style on that proxy.

Start by reproducing the repeated “Add post” behavior at the linked ZeroNet proxy blog and compare it with the proxy project referenced in the issue. Determine the intended multi-user boundary and verify that unsigned edits cannot pollute the proxy or affect other users; the issue is done when those effects are prevented.

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