Bound the holder's measuring; dump the database platform (hq ADR 0233)

Walks run at most daily and stop after ten minutes or two million files; datasets are read from
their counters and large items from their top level only. The database platform's tables are
dumped with pg_dumpall rather than copied as live files.

modules/supabase/module.json

@@ -64,7 +64,17 @@
         "id": "db",
         "path": "${dir:db-data}",
         "class": "valuable",
-        "why": "every table; copied as live files, which may not restore \u2014 a dump is wanted"
+        "backup": {
+          "dump": "docker exec supabase-db pg_dumpall -h 127.0.0.1 -U supabase_admin > ${dir:dumps}/all.sql.partial && mv ${dir:dumps}/all.sql.partial ${dir:dumps}/all.sql",
+          "into": "dumps"
+        },
+        "why": "every table; copied by pg_dumpall inside the database's container (local connections are trusted there), since a running store's files are not a consistent copy"
+      },
+      {
+        "id": "dumps",
+        "path": "${dir:dumps}",
+        "class": "rebuildable",
+        "why": "last night's dump of the database, made again every night"
       },
       {
         "id": "storage",
@@ -111,6 +121,12 @@
       "mode": "0700",
       "owner": "105:106"
     },
+    {
+      "id": "dumps",
+      "type": "directory",
+      "path": "${dir:state}/dumps",
+      "mode": "0700"
+    },
     {
       "id": "db-config",
       "type": "directory",