feat: Add Cantaloupe sync API with staged import workflow

- New cantaloupe_sync.py module with complete pipeline
- Heuristic Excel column mapping (20+ keyword patterns)
- Diff engine: detects new/changed/removed/unchanged assets
- 5 API endpoints: sync, list batches, view batch, approve, reject
- cantaloupe_sync_batches table with status workflow
- Admin server port changed to 8090
- openpyxl added to requirements.txt

run.sh

@@ -5,9 +5,8 @@ set -euo pipefail
 
 PORT="${PORT:-8090}"
 HOST="${HOST:-0.0.0.0}"
-CANTEEN_DB_PATH="${CANTEEN_DB_PATH:-$(dirname "$0")/../canteen-asset-tracker/assets.db}"
 
-exec env CANTEEN_DB_PATH="$CANTEEN_DB_PATH" python -m uvicorn admin_server:app \
+exec python -m uvicorn admin_server:app \
   --host "$HOST" \
   --port "$PORT" \
   --reload \