Add Windows process memory support

[rushikeshsakharleofficial]

Summary

• Add native Windows process enumeration and memory accounting using PSAPI/kernel32 through ctypes
• Preserve the existing Linux/FreeBSD /proc implementation
• Add Windows-compatible handling for -p, -s, -d, -t, -w, and accepted-but-ignored -S
• Print best-effort totals on Windows, with a warning when shared memory may be over-estimated
• Document Windows usage and standalone .exe builds with PyInstaller

Notes

• Windows swap usage is not reported, so -S/--swap is accepted for compatibility but does not print a fake zero-valued swap column.
• Some protected Windows processes may require fallback memory counters, so totals can be slightly high.

Testing

• python ps_mem.py --help
• python ps_mem.py --version
• python ps_mem.py -p $PID
• python ps_mem.py -s -p $PID
• python ps_mem.py -d -p $PID
• python ps_mem.py -t
• python ps_mem.py -S -p $PID
• python ps_mem.py -t -S
• python ps_mem.py -p nope
• python ps_mem.py -w 0
• one-iteration -w 1 smoke test
• python -m py_compile ps_mem.py
• git diff --check