ISSUE-023 — Delete empty `src/` tree and production Docker cleanup

[shivaram19]

• Functional surgeon view: The Docker image does not ship runtime artifacts or dead code.
• Acceptance criteria:
  1. src/ removed.
  2. .dockerignore excludes data/*_raw.html, output/*.json, __pycache__.
  3. Image size reduction measured.
• Dependencies: ISSUE-022 (refactor accepted).