The MEDIA_TAG_CLEANUP_RE and extract_local_files path regex both used
(?:~/|/) to anchor paths, which only matches Unix-style absolute and
home-relative paths. Two additional _TOOL_MEDIA_RE patterns in run.py
had the same limitation. Windows absolute paths (C:\Users\..., D:/...)
were silently ignored, causing MEDIA directive delivery to fail.
Add [A-Za-z]:[/\\] as a third anchor alternative in all four regex
locations (base.py x2, run.py x2). Also update path separators in
extract_local_files from / to [/\\] so it can traverse Windows
directory trees.
Revert accidental + quantifier in MEDIA_TAG_CLEANUP_RE lookahead
that changed match-one to match-one-or-more (unrelated to fix).
Fixes: #34632
