GHSA-7prp-2623-8g45: djust has an unauthenticated arbitrary module import via the WebSocket/SSE view-mount path

### Impact The djust live transport resolves the LiveView to mount from a **client-supplied dotted path** by calling `__import__(module_path, ...)`. The module is imported — running its **top-level code (import side effects)** — *before* the framework checks that the resolved object is a `LiveView` subclass and *before* any per-view authentication. The `LIVEVIEW_ALLOWED_MODULES` allowlist that should contain this is **fail-open** (`if allowed_modules:` — skipped when the setting is unset, the framework default) and uses loose `startswith` matching. …