Replace heavy TUI with styled CLI and add multi-file scan mode

- Remove ratatui/crossterm TUI (859 lines) in favor of lightweight
  console + indicatif styled output with live progress bars
- Add -a/--all flag to scan all files in a directory matching extensions
- Add -x/--extensions flag for custom comma-separated extensions
- Add --dir flag to specify scan directory (defaults to current dir)
- Add interactive prompt mode when run with no arguments
- Fix panic on empty input files (chunk size zero)
- Same visual design for both CLI and interactive modes
- Bump version 0.2.0 → 0.3.0

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: sinescode