Add project menu and editor shell UI

[dobutro]

Motivation

• Provide an initial project selection and creation UX so users can choose or create a mod project without writing code.
• Enforce an internal project name policy (required, lowercase english letters and _, unique) that will be used to generate project files.
• Offer a full-screen editor shell that opens after project creation so future tooling can be plugged into the editor area.

Description

• Added index.html which contains the project menu layout, creation form (display name optional, internal appName required), project list and an editor placeholder section.
• Added styles.css implementing the dark/grey theme with lime accents and all layout/styles for menu, cards, form and editor states.
• Added script.js which implements project lifecycle helpers including loadProjects, saveProjects, validation via validateAppName, project creation (finalizeProject), localStorage persistence under the key fortify-mods-projects, and menu/editor toggling (openEditor / closeEditor).
• Created project object metadata including id, displayName, appName, image, createdAt, and projectFile (set to ${appName}.fortify) when a project is created.

Testing

• Served the static files with python -m http.server 8000 and ran a Playwright script that navigated to http://127.0.0.1:8000/index.html and saved a screenshot; the screenshot artifact fortify-menu.png was produced successfully.
• Verified that files were added to the repo and a commit was created; the commit succeeded.
• No unit tests were added or run for frontend logic; interactive/manual verification via the screenshot was performed and succeeded.

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Codex Task