Phase 1: FastAPI backend with async job model

- backend/app: FastAPI API wrapping the CAD skill modules
  - upload -> job -> poll -> model / BOM / artifacts -> geometry query
  - SQLite via SQLModel (Model, Job, BomRow, QueryLog)
  - ThreadPoolExecutor worker, serialized, with live stage updates
- docker-compose.yml: dev server (mounts source, --reload) on :8000
- api-test.sh: end-to-end live validation script
- requirements.txt: add fastapi, uvicorn, python-multipart, sqlmodel
- external_diagram.py: port active-area detection OCC.Core -> OCP
- .gitignore, PHASE1.md

Validated live: MR16 round-trip passes (28 BOM rows, 12 artifacts,
bounding-box query, xlsx download; active-area detection working).

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

api-test.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# Phase 1 live validation — exercises the API end to end against a running server
+# (docker compose up). Upload a sample, poll the job, read model detail, download
+# an artifact, run a geometry query.
+#
+#   docker compose up -d && ./api-test.sh
+set -uo pipefail
+cd "$(dirname "$0")"
+
+BASE="${BASE:-http://localhost:8000}"
+SAMPLE="${SAMPLE:-skill.src/MR16s Gen1_EN.step}"
+PYJ() { python3 -c "import sys,json$1"; }   # tiny JSON helper
+
+echo "== health =="
+curl -fsS "$BASE/api/health"; echo
+
+echo "== upload ($SAMPLE) =="
+resp=$(curl -fsS -F "file=@${SAMPLE}" -F "diagram=true" "$BASE/api/upload")
+echo "$resp"
+job_id=$(PYJ ";print(json.load(sys.stdin)['job_id'])" <<<"$resp")
+model_id=$(PYJ ";print(json.load(sys.stdin)['model_id'])" <<<"$resp")
+
+echo "== poll job $job_id =="
+status=""
+for i in $(seq 1 200); do
+  j=$(curl -fsS "$BASE/api/jobs/$job_id")
+  status=$(PYJ ";print(json.load(sys.stdin)['status'])" <<<"$j")
+  stage=$(PYJ ";print(json.load(sys.stdin).get('stage'))" <<<"$j")
+  echo "  [$i] status=$status stage=$stage"
+  [ "$status" = "done" ] && break
+  [ "$status" = "error" ] && { echo "$j"; exit 1; }
+  sleep 3
+done
+[ "$status" = "done" ] || { echo "TIMEOUT waiting for job"; exit 1; }
+
+echo "== model $model_id detail =="
+detail=$(curl -fsS "$BASE/api/models/$model_id")
+echo "$detail" | PYJ "
+d=json.load(sys.stdin); m=d['model']
+print('  backend:', m['backend'], '| faces:', m['face_count'], '| parts:', m['part_count'])
+print('  bbox(mm):', m['bbox_x_mm'], m['bbox_y_mm'], m['bbox_z_mm'], '| chinese:', m['has_chinese'])
+print('  bom rows:', len(d['bom']))
+print('  artifacts:', d['artifacts'])
+"
+
+echo "== download .xlsx artifact =="
+art=$(echo "$detail" | PYJ ";print(next((a for a in json.load(sys.stdin)['artifacts'] if a.endswith('.xlsx')),''))")
+if [ -n "$art" ]; then
+  enc=$(python3 -c "import urllib.parse,sys;print(urllib.parse.quote(sys.argv[1]))" "$art")
+  curl -fsS -o /tmp/api_test_bom.xlsx "$BASE/api/models/$model_id/artifacts/$enc"
+  echo "  downloaded '$art' -> $(wc -c < /tmp/api_test_bom.xlsx) bytes"
+else
+  echo "  no .xlsx artifact found"; exit 1
+fi
+
+echo "== geometry query =="
+curl -fsS -X POST -H 'Content-Type: application/json' \
+  -d '{"query":"bounding box"}' "$BASE/api/models/$model_id/query" \
+  | PYJ ";print(json.load(sys.stdin)['result'][:500])"
+
+echo "== API TEST PASSED =="