Fix welcomebot-signups: heredoc instead of -c string to avoid bash/python quote clash

bin/welcomebot-signups

@@ -52,11 +52,11 @@ if ! docker inspect "$CONTAINER" >/dev/null 2>&1; then
   echo "welcomebot-signups: container '$CONTAINER' not found (is it deployed/running?)" >&2; exit 1
 fi
 
-docker exec \
+docker exec -i \
   -e SIG_LIMIT="$limit" \
   -e SIG_FLAGGED_ONLY="$flagged_only" \
   -e SIG_ACCT="$acct_filter" \
-  "$CONTAINER" python3 -c '
+  "$CONTAINER" python3 <<'PYEOF'
 import os
 import sqlite3
 
@@ -81,7 +81,11 @@ rows = conn.execute(sql, params).fetchall()
 if not rows:
     print("(no matching signup records)")
 for acct, ip, classification, org, flagged, ipblock, ts in rows:
+    acct = acct or ""
+    ip = ip or ""
+    classification = classification or ""
+    org = org or ""
     flag = "FLAGGED" if flagged else "-"
     ipb = "ipblock=yes" if ipblock else "ipblock=no"
-    print(f"{ts}  {acct or '':20s} {ip or '':16s} {classification or '':12s} {flag:8s} {ipb:12s} {org or ''}")
-'
+    print(f"{ts}  {acct:20s} {ip:16s} {classification:12s} {flag:8s} {ipb:12s} {org}")
+PYEOF