fix: read URLs from environment variables instead of hardcoded values

[cfsmp3]

Summary

Fix frontend to read backend/frontend/container URLs from environment variables instead of using hardcoded localhost values.

Problem

The URLs.ts file had hardcoded values:

backendURL: 'http://localhost:8000/',
frontendURL: 'http://localhost:80',
containerOrigin: 'http://localhost:8080/',

This meant the VITE_BACKEND_URL, VITE_FRONTEND_URL, and VITE_CONTAINER_ORIGIN environment variables in .env files were completely ignored, making production deployment impossible without code changes.

Solution

Use Vite's import.meta.env to read environment variables at build time, with localhost fallbacks for development:

backendURL: import.meta.env.VITE_BACKEND_URL || 'http://localhost:8000/',
frontendURL: import.meta.env.VITE_FRONTEND_URL || 'http://localhost:80',
containerOrigin: import.meta.env.VITE_CONTAINER_ORIGIN || 'http://localhost:8080/',

Test plan

• Verified localhost defaults still work for development
• Verified production deployment with custom URLs works when .env is present during build

🤖 Generated with Claude Code

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