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

internal/bootstrap/builder.go

@@ -53,7 +53,7 @@ func InstallBuilder(ctx context.Context, o Options, d Deps, control controlPlane
 			"This is the manifest that makes the builder an ordinary module. Without it the mesh "+
 			"has the image and no way to run it, so nothing can be built here", err)
 	}
-	pinned, places, err := pinImage(manifest, published.Reference)
+	pinned, places, err := pinImage(manifest, published.Reference, BuilderModule)
 	if err != nil {
 		return out, err
 	}