Client mass-assignment of arbitrary view attributes via the default dj-model update_model handler

Summary

djust provides Phoenix LiveView-style reactive server-side rendering for Django with Rust-powered performance. Prior to version 1.0.7, `djust.mixins.model_binding.ModelBindingMixin` provides a default `update_model` event handler and is part of the LiveView base MRO, so every LiveView exposes it. It `setattr`s a view attribute whose name is client-supplied (`field`), gated only by: reject `_`-prefixed names; reject a 14-entry denylist of framework internals (`FORBIDDEN_MODEL_FIELDS`); optional `allowed_model_fields` which defaults to None = allow all; and `hasattr` existence. As a result, a client can set any public, existing view attribute — not just the fields actually bound with `dj-model=` in the rendered template. The denylist covers framework plumbing but nothing about developer business/authz state, and the allowlist is opt-in (off by default). A developer who binds one `dj-model="search"` input and also keeps `self.account_id` / `self.is_admin` / `self.total_price` as view state does not realize a client can set ALL of them via `{type:event, event:"update_model", params:{field, value}}` over the WebSocket. Type coercion matches the target attribute's type (so `"true"` -> bool True), aiding the attacker. This issue is fixed in djust 1.0.7. As a workaround, set `allowed_model_fields` explicitly on every view using dj-model (or subclassing LiveView) to the minimal list of bindable fields; do not keep authorization/ownership state in public view attributes that share the view with dj-model bindings.