fix(docs): use utf-8 for redirect generation

[Rolly Calma (Ghraven)]

Summary

• Read the redirect template and URL list with explicit UTF-8 encoding.
• Write generated redirect pages with explicit UTF-8 encoding.

Problem

The redirect generation utility currently depends on Python's locale default encoding for text file I/O. That can be inconsistent on Windows and other environments where the locale is not UTF-8.

Before / after

Before, redirect generation used the platform default encoding. After, the same files are read and written as UTF-8 explicitly, making generated docs redirects more reproducible across environments.

Verification

• python -m py_compile python\\docs\\redirects\\redirects.py
• python python\\docs\\redirects\\redirects.py $env:TEMP\\autogen_redirect_smoke
• Checked generated index.html and docs\\Getting-Started\\index.html existed in the temp output folder.
• git diff --check

Thank you for maintaining AutoGen.