enhance: Replace print() with logging

[anidixit64]

title: "Replace print Commands with Logging"

Acceptance Criteria

A checklist of conditions that must be met for this feature to be considered complete.

• At the top of parser.py, add import logging.
• Create a module-level logger: log = logging.getLogger(name).
• Search for all instances of print(f"Warning: ...") in the file.
• Replace each one with an appropriate log.warning() or log.error() call, using format strings for variables.
  • Example in parse_epub: log.warning("Could not parse chapter %s: %s", href, e)
  • Example in _extract_chapter_titles: log.warning("Could not extract chapter titles...: %s", e)

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Definition of Done

• Feature implemented as per Acceptance Criteria
• All new code is covered by pytest tests
• Ensure >90% coverage on the changed or new code
• Documentation (docstrings and Sphinx docs) is updated
• The pre-commit hooks pass on all changed files