Silent failure when passing a directory as input

[LuBashQ]

Summary

Addresses and closes #208.

• Add requirement to image argument to be a file (or a symbolic link to a file), preventing accidentally passing directories
• Add file name and line number to log entries

Type of change

• Bug fix
• Feature
• Refactor
• Breaking change
• This change requires a documentation update
• This change contains modifications to the --help output
  • I ran scripts/regenerate_readme.py from the root directory to ensure it has the latest sample output

Test plan

Try to burn a directory, and it should fail with the following error

$ caligula burn --force --compression none --hash skip -o /dev/sda /tmp/caligula-668102-1766420269461/
error: invalid value '/tmp/caligula-668102-1766420269461/' for '<IMAGE>': path is not a file or symlink to a file

For more information, try '--help'.

Log files should contain the file and line number where it was generated

$ cat /tmp/caligula-1027724-1766426069683/log/main.log 
2025-12-22T17:54:29.683412Z  INFO caligula::tty: src/tty.rs:14: attempting to store terminal state before program started
2025-12-22T17:54:29.683424Z DEBUG caligula::ui::main: src/ui/main.rs:35: Starting primary process
...