chore(demo): add new env vars

[overbalance]

What problem is this solving?

Update demo app configuration for custom data and config endpoints to match .env.template.

Short description of changes

• Added VITE_DATA_URL and VITE_CONFIG_URL env var placeholders to demo setup script

Testing

• Verified script generates correct .env template

[github-actions]

Chrome DevTools Protocol Tracing (Script: 96.51ms, Heap: 14.50MB)

	Number of Requests	Size of Requests	Script Duration	Task Duration	Heap Used Size
Requests	+3 requests	+29.69 KB
Page Loaded			+15.44 ms	+7.66 ms	+0.94 MB
Generate 100 fetch requests			+8.69 ms	+45.13 ms	+2.27 MB
Generate 100 XHR requests			+35.74 ms	+94.31 ms	+2.46 MB
Click 100 buttons and generate 100 logs			+29.33 ms	+36.63 ms	+3.04 MB
Throw a 100 exceptions			+0.41 ms	+13.03 ms	+2.62 MB
End Session			+6.88 ms	+14.36 ms	+3.18 MB
Total	+3 requests	+29.69 KB	+96.51 ms	+211.11 ms	+14.50 MB

Lighthouse (Script Eval: 48.77ms)

	Difference	Description
Total Blocking Time	0 ms	Difference in Total Blocking Time: Sum of all time periods between FCP and Time to Interactive, when task length exceeded 50ms, expressed in milliseconds. Learn more about the Total Blocking Time metric.
Main Thread Time	+43.37 ms	Difference in Main Thread Time: Consider reducing the time spent parsing, compiling and executing JS. You may find delivering smaller JS payloads helps with this. Learn how to minimize main-thread work
Script Evaluation Time	+48.77 ms	Difference in Script Evaluation Time: Consider reducing the time spent parsing, compiling, and executing JS. You may find delivering smaller JS payloads helps with this. Learn how to reduce Javascript execution time.

Platform Tests (vite-7 gzip: 47.99KB)

vite-7 Platform Tests

	Total Uncompressed Size	Total Gzip Size
vite-7 - esnext	+164.67 KB	+47.99 KB
vite-7 - es2015	+171.51 KB	+49.67 KB

vite-otel-latest Platform Tests

	Total Uncompressed Size	Total Gzip Size
vite-otel-latest - esnext	+163.74 KB	+49.69 KB
vite-otel-latest - es2015	+170.50 KB	+51.32 KB

webpack-5 Platform Tests

	Total Uncompressed Size	Total Gzip Size
webpack-5 - esnext	+121.11 KB	+43.17 KB
webpack-5 - es2015	+122.22 KB	+44.65 KB