Add standalone Electron wrapper for HostAdmin

[Copilot]

Modernize HostAdmin by enabling a standalone desktop experience using a modern JS runtime (Electron), while keeping the existing extension UI and logic intact.

• Electron wrapper + glue
  • Add minimal Electron main/preload/bridge and platform adapters to reuse core/editor.html without extension APIs.
  • Update glue resolution to select the right HostAdmin host across Chrome/Firefox/Electron safely.
• Security hardening
  • Disable Node integration in the renderer and validate IPC payloads (size + null-byte checks).
  • Normalize line endings before writes in the Electron host file adapter.
• Docs and build hygiene
  • Document Electron start path in README and ensure dist script ignores node_modules.

Example (Electron IPC guard + size limit):

const MAX_HOSTS_SIZE = 1024 * 1024;
const isValidHostsData = (data) =>
  typeof data === 'string' && data.indexOf('\0') === -1 && data.length <= MAX_HOSTS_SIZE;

Screenshot:

Original prompt

modernize this using latest js tech
running with standalone electron? or samilar framework

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