fix(maintenance): harden cache cleanup against broad deletion and improve file organizer safety

[ashishsinghbora]

Summary

cleanup-cache.sh

• Removed redundant duplicated code block and fixed typo in redirect syntax (dev/null -> /dev/null).
• Eliminated unconditional broad rm -rf /tmp deletion to protect active user sessions, sockets, and locks.
• Added user confirmation prompt, -n / --dry-run inspection, and -y / --yes auto-confirmation.
• Added cache inspection and safe cleanup for user thumbnail cache (~/.cache/thumbnails) and user trash.
• Added comprehensive cache usage detection across pacman, apt, dnf, zypper, apk, and systemd journal.

file-organizer.sh

• Added guards preventing accidental execution on root / and $HOME root.
• Safely skips symbolic links to prevent breaking relative links or dangling targets.
• Preserves hidden files, files without extensions, and avoids overwriting existing destination files.
• Added markdown (.md) to documents and expanded archive/audio formats.

Verification

• Tested dry-run and live file organization with spaces, Unicode characters, collisions, hidden files, and symlinks.
• Tested dry-run and live cache cleanup with mock temporary HOME.
• Verified ShellCheck passes without warnings.
• Verified test suite passes.

[ashishsinghbora]

Code review: verified safe user cache cleanup replacing broad /tmp deletion, verified symlink and collision handling in file organizer, and confirmed all tests pass.