Initial commit: Conflict Checker

Cross-discipline design-contradiction checker for construction drawing
sets. Standalone tool broken out from Iron_Bid; a pipeline stage may
later fold back into Iron_Bid.

Pipeline: PDF->images -> per-sheet assertion extraction -> deterministic
clustering by location -> per-cluster reasoning -> report.
Includes CLI (cli/run_check.py) and web UI (backend/main.py).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/.llm_cache/32e387c76f4be36e8ed98de081c724f184bfac20005ed0f109e27de2c2132c86.json

@@ -0,0 +1 @@
+{"sheet_number": null, "discipline": "Unknown", "sheet_title": "Page 14 (extraction failed)", "level": null, "scale": null, "assertions": []}