refactor: replace Electron webview with iframe and bump to v2026.4.303}
- Replace deprecated Electron <webview> tag with <iframe> for loading the Redis UI - Switch from executeJavaScript() to postMessage() for cross-frame communication (set-language, menu) - Simplify server readiness logic: replace complex retry/reload/shell-auto-reload with a straightforward waitForServer polling loop before setting iframe src - Remove webviewTag webPreference and did-attach-webview handler from window creation - Fix external link handler to return { action: 'deny' } after opening in system browser - Update Content-Security-Policy to add frame-src directive for iframe support - Change onload.mjs from ES module script to regular script with IIFE wrapper and top-level error handling - Add asarUnpack for p3x-redis-ui-material/dist to support iframe file access - Bump p3x-redis-ui-material to ^2026.4.304 and p3x-redis-ui-server to ^2026.4.301 - Update version to v2026.4.303 across README, changelogs, and package.json - Add v2026.4.303 changelog entry with feature, perf, bugfix, refactor, and docs summaries