Three-layer dedup check before community post submission:
- L1: title ILIKE search against existing posts in community DB
- L2: Jaccard ingredient overlap using local corpus (≥0.70 very_similar, ≥0.35 somewhat_similar)
- L3: similar_to_ref FK — user can explicitly mark post as variation of existing
New endpoint: POST /api/v1/community/check-similar (gracefully no-ops if community DB absent)
New service: app/services/community/dedup.py — jaccard(), similarity_tier(), build_similar_post_result()
Both publish modals (plan + outcome) now check similarity before submit; user can proceed as-is,
mark as variation, or cancel. similar_to_ref passed in final publish payload.
