Fix invalid escape sequence warnings

[Mirochill]

Description

Fix Python 3.13+ SyntaxWarning: invalid escape sequence warnings reported in #561.

The patch:

• escapes the Windows path separator example in the package docstring;
• makes the git branch status regex a raw string while keeping the same pattern;
• makes the uptime segment regexes raw strings as they had the same invalid escape pattern.

Fixes: #561

Validation

Not run locally.

Static validation run:

• git diff --check HEAD~1..HEAD

I opened this as a draft because I do not see GitHub Actions checks for this repository; if remote CI appears, I will use that signal before marking it ready.