[v4] Implement predatory journal flagging

[cpitzi]

Summary

Identify references citing journals classified as predatory or questionable by established assessment methodologies.

See roadmap/v4-features.md (Priority 3) for full specification.

Open Questions

• Data source: Cabells Predatory Reports is the gold standard but is commercial. Is API access feasible? Cost?
• Alternative sources: Beall's List (archived, not maintained), community lists, DOAJ membership as positive signal
• Classification language: "Predatory" is contentious. Should the auditor use "potentially predatory," "not indexed in DOAJ," or another framing?

Implementation Approach

1. Check journal against known predatory journal databases/lists via web search
2. Check DOAJ membership as a positive legitimacy signal
3. Check Scopus/PubMed indexing as additional legitimacy signals
4. Flag journals that appear on predatory lists or lack any recognized indexing

Acceptance Criteria

• Identifies journals on known predatory lists
• Distinguishes "confirmed predatory" from "potentially predatory"
• Does not flag journals removed from predatory lists after improvement
• Handles journal name variations (predatory journals frequently rename)
• Classified as Elevated risk (not High — the cited paper may still be legitimate research)

Dependencies

• Requires resolution of the data source question before implementation