Phase 3.1: adopt the foundation store as the postgres module

InstallStore turns the mesh-store the foundation raised at genesis into the
postgres module, adopted in place: it verifies the module's server names the
same container and the same image the foundation is running (fail-fast on a
drift, rather than tearing down the mesh's store), then registers, builds the
provisioner, and carries the superuser in via secret accept — the mesh cannot
invent a credential that already made the databases (mirroring the control
plane's store-connection delivery, control.go). pinImage generalised to any
module for reuse.

Issue 051 (WBS 3.1). One server holds the controller's contexts and every
module's database.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx

examples/foundation-first-node.lock

@@ -55,7 +55,7 @@
         "POSTGRES_PASSWORD": "bootstrap",
         "PGDATA": "/var/lib/postgresql/data/pgdata"
       },
-      "ports": ["127.0.0.1:5432:5432"],
+      "ports": ["5432:5432"],
       "volumes": ["mesh-store-data:/var/lib/postgresql/data"]
     },
     // Over TCP, not the socket. While the store initialises it runs a temporary server on the