Add `.editorconfig` to standardize formatting across contributions

[sergio-sisternes-epam]

Context

In #653, a contributor noted there is no .editorconfig in the repo and a mix of "trim trailing whitespace" vs "leave trailing whitespace" in the code. Their editor was set to trim, resulting in significant whitespace noise in an otherwise surgical PR (+404/-331 total, ~93 substantive lines).

Problem

Without an .editorconfig, contributors' editors apply inconsistent formatting (trailing whitespace, final newlines, indent style) which inflates diffs and makes code review harder.

Proposal

Add a root .editorconfig with sensible defaults:

• trim_trailing_whitespace = true
• insert_final_newline = true
• indent_style = space
• indent_size = 4 for Python, 2 for YAML/JSON/MD
• charset = utf-8
• end_of_line = lf

This should be a standalone formatting commit (no logic changes) so the whitespace normalization is isolated from feature work.

References

• Enable SSH timeout to fallback to HTTP. #653 — PR where this was identified