Improve: shred files and wipe disks

- Reorganize content with clear sections and improved flow
- Add detailed HDD vs. SSD comparison with wear leveling and TRIM explanation
- Expand file shredding limitations to cover journaling filesystems and NTFS MFT
- Add "haystack approach" section explaining Chaff feature
- Convert myths to table format for clarity
- Rewrite practical tips with SSD-specific guidance
- Improve readability with shorter paragraphs and better formatting
- Replace DBAN with ShredOS

Author: az0