refactor: make frontend icons canonical

[willchen96]

Summary

• move the canonical SVG set into frontend/public/icons
• remove the shared icon package and frontend copy script
• point the Word add-in Webpack alias at the frontend public icon directory
• remove icon sync hooks from frontend lifecycle commands

Why

Next.js already requires these assets under public to serve the existing /icons URLs. Keeping that directory canonical removes generated-file synchronization while preserving all frontend URLs and Word add-in imports.

Verification

• Frontend icon-focused tests: 4 files, 18 tests passed
• Word add-in application and E2E TypeScript checks passed
• Word add-in Webpack development build passed and emitted 16 content-hashed SVG assets
• git diff --check passed

The production Word wrapper was also invoked, but correctly stopped before Webpack because deployment environment variables were not supplied.