Add Ctrl+E shortcut to focus Blockly workspace

[tracygardner]

Motivation

• Provide a keyboard shortcut (Ctrl/Cmd + E) to move focus back to the Blockly code workspace so users can quickly resume block editing and have Blockly restore any previously passive/secondary focus inside the workspace via Blockly's focus manager.

Description

• Add a global shortcut handler for Ctrl+E in main/main.js which calls Blockly.getFocusManager()?.focusTree?.(workspace) to restore workspace focus and preserve keyboard-navigation state.
• Update the keyboard shortcut help table in index.html to include a Ctrl + E row labeled Focus code workspace.
• Add a keyboard_workspace_ui translation key to the locale files (locale/*.js) so the new help entry resolves through the existing data-i18n mechanism and falls back properly.

Testing

• Ran npm run build; this run failed due to a pre-existing unrelated Blockly import issue ("DUMMY_INPUT" is not exported by node_modules/blockly/index.mjs).
• Ran npx eslint main/main.js locale/*.js; linting failed due to existing project issues (duplicate locale keys and some existing main/main.js warnings/errors) unrelated to the new shortcut code.
• Started the dev server and executed a Playwright script that loaded the app and captured a screenshot of the info panel showing the new Ctrl + E row, which completed successfully and confirms the UI update.

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Codex Task