feat(ops): answer "what datastore does this app actually use?"

scripts/hetzner/data-deps.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# data-deps.sh — which datastore does each app on the box ACTUALLY use?
+#
+# WHY THIS EXISTS: on 2026-08-29 the question "is anything still using the
+# Supabase stack?" was answered by grepping DATABASE_URL across every app env.
+# Every hit pointed at localhost:5432, so the answer looked like "nothing" —
+# and stopping the stack was one command from taking orangecat and botsmann
+# down, with 114 auth users and 927 messages behind it.
+#
+# The reasoning error: a Supabase app never sets DATABASE_URL. It talks HTTPS
+# to PostgREST/Kong via SUPABASE_URL. The absence of a Postgres connection
+# string is not the absence of a dependency — it is the signature of a
+# DIFFERENT one. Grepping for one binding and concluding "unused" reads
+# absence as an answer.
+#
+# It also reports whether a Postgres target actually holds tables, because an
+# empty database is worse than a missing one: `orangecat` exists in the native
+# cluster with ZERO tables, a leftover pointing nowhere, and a reader who sees
+# the name assumes the app lives there.
+#
+# Usage: bash data-deps.sh    (read-only; answers "is X safe to stop?")
+set -u
+export LC_ALL=C
+
+# strip: key=, quotes, scheme, then CREDENTIALS (everything up to the last @),
+# then any query string. Order matters — stripping the path before the
+# credentials mangles a postgres URL into the scheme.
+hostof() { sed 's#^[^=]*=##; s#^"##; s#"$##; s#^[a-z+]*://##; s#^.*@##; s#?.*$##'; }
+hostonly() { hostof | sed 's#/.*##'; }
+
+printf '%-22s %-34s %-26s %s\n' APP POSTGRES SUPABASE VERDICT
+printf '%-22s %-34s %-26s %s\n' "---" "---" "---" "---"
+for d in /opt/*/; do
+  app=$(basename "$d")
+  case "$app" in _appcron|backups|monitoring|supabase) continue ;; esac
+  f="$d/shared/.env"; [ -f "$f" ] || f="$d/app/.env"; [ -f "$f" ] || continue
+  # app/.env may be a symlink to shared/.env; reading one is enough either way.
+
+  pg=$(grep -m1 '^DATABASE_URL=' "$f" 2>/dev/null | hostof)
+  sb=$(grep -m1 -E '^(NEXT_PUBLIC_)?SUPABASE_URL=' "$f" 2>/dev/null | hostonly)
+
+  # does the postgres target actually contain anything?
+  pgnote=""
+  if [ -n "$pg" ]; then
+    db=${pg##*/}
+    n=$(sudo -u postgres psql -d "$db" -tAc \
+        "select count(*) from information_schema.tables where table_schema='public';" 2>/dev/null | tr -d ' ')
+    [ -n "$n" ] && [ "$n" = "0" ] && pgnote=" [EMPTY — decoy]"
+  fi
+
+  if   [ -n "$sb" ] && [ -n "$pg" ]; then v="supabase (postgres var is a fossil)"
+  elif [ -n "$sb" ];                 then v="supabase"
+  elif [ -n "$pg" ];                 then v="native postgres"
+  else                                    v="no datastore configured"
+  fi
+  printf '%-22s %-34s %-26s %s\n' "$app" "${pg:-—}$pgnote" "${sb:-—}" "$v"
+done