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/.env.example

@@ -0,0 +1,30 @@
+# Copy to backend/.env and fill in your OpenRouter key.
+
+AI_BASE_URL=https://openrouter.ai/api/v1
+AI_API_KEY=sk-or-...
+MODEL=google/gemini-2.5-pro
+
+# Pipeline tuning
+PDF_DPI=100
+MAX_PAGES=60
+MAX_DIMENSION=2400
+LLM_TIMEOUT=180
+EXTRACT_MAX_TOKENS=8192
+REASON_MAX_TOKENS=4096
+EXTRACT_CONCURRENCY=4
+REASON_CONCURRENCY=4
+
+# Public URL users reach this server on (used for the link in result emails)
+APP_BASE_URL=http://localhost:8099
+
+# Email notifications (optional). Leave SMTP_HOST blank to disable.
+# Examples:
+#   Gmail:  SMTP_HOST=smtp.gmail.com  SMTP_PORT=587  (use an App Password)
+#   M365:   SMTP_HOST=smtp.office365.com  SMTP_PORT=587
+SMTP_HOST=
+SMTP_PORT=587
+SMTP_USER=
+SMTP_PASSWORD=
+SMTP_FROM=
+SMTP_USE_TLS=true
+SMTP_USE_SSL=false