feat: add PostgREST image registry and schema/role preflight

- Pin postgrest image to ghcr.io/pgedge/postgrest:14.5
- Extend version pattern to accept two-part versions (e.g. 14.5)
- Add ValidatePostgRESTPrereqs activity with Patroni primary
  discovery and reachable-instance fallback
- Fail fast on invalid PostgREST config before plan step
- All config fields optional: db_schemas defaults to "public",
  db_anon_role to "pgedge_application_read_only"

PLAT-499, PLAT-500

Author: moizpgedge

api/apiv1/design/database.go

@@ -9,7 +9,7 @@ const (
 	cpuPattern             = `^[0-9]+(\.[0-9]{1,3}|m)?$`
 	postgresVersionPattern = `^\d{2}\.\d{1,2}$`
 	spockVersionPattern    = `^\d{1}$`
-	serviceVersionPattern  = `^(\d+\.\d+\.\d+|latest)$`
+	serviceVersionPattern  = `^(\d+\.\d+(\.\d+)?|latest)$`
 )
 
 var HostIDs = g.ArrayOf(Identifier, func() {
@@ -143,10 +143,10 @@ var ServiceSpec = g.Type("ServiceSpec", func() {
 		g.Meta("struct:tag:json", "service_type")
 	})
 	g.Attribute("version", g.String, func() {
-		g.Description("The version of the service in semver format (e.g., '1.0.0') or the literal 'latest'.")
+		g.Description("The version of the service (e.g., '1.0.0', '14.5') or the literal 'latest'.")
 		g.Pattern(serviceVersionPattern)
 		g.Example("1.0.0")
-		g.Example("1.2.3")
+		g.Example("14.5")
 		g.Example("latest")
 		g.Meta("struct:tag:json", "version")
 	})

api/apiv1/gen/control_plane/service.go

@@ -521,7 +521,7 @@ func validateS3RepoProperties(props repoProperties, path []string) []error {
 }
 
 var pgBackRestOptionPattern = regexp.MustCompile(`^[a-z0-9-]+$`)
-var semverPattern = regexp.MustCompile(`^\d+\.\d+\.\d+$`)
+var semverPattern = regexp.MustCompile(`^\d+\.\d+(\.\d+)?$`)
 
 // reservedLabelPrefix is the label key prefix reserved for system use.
 const reservedLabelPrefix = "pgedge."

api/apiv1/gen/http/control_plane/client/types.go

@@ -803,6 +803,16 @@ func TestValidateServiceSpec(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "valid PostgREST service with two-part version",
+			svc: &api.ServiceSpec{
+				ServiceID:   "postgrest",
+				ServiceType: "postgrest",
+				Version:     "14.5",
+				HostIds:     []api.Identifier{"host-1"},
+				Config:      map[string]any{},
+			},
+		},
 		{
 			name: "valid MCP service with 'latest' version",
 			svc: &api.ServiceSpec{