feat(templates): v2 — multi-service graph templates, expressions, compose import

Config v2 adds services[] to TemplateConfig: members declare key, type
(web|worker|cron|database), runtime, environment, volumes and depends_on.
Deploy topo-sorts the graph, creates databases first (managed DBs attached
to the project network under their key as DNS alias), then services with
resolved env, and enqueues a real deployment per service.

Expressions: {{secret}}, {{secret(N)}}, {{random:N}}, {{VAR}},
{{VAR:-default}} and {{service.<key>.<prop>}} with props host, port, url,
user, password, database. Credential-bearing refs (password/url) mark the
consuming variable secret — stored encrypted, masked in plan output.
Single-service template secret vars are now encrypted at rest too.

New endpoints: POST /templates/:id/plan (dry-resolve with missing/
unresolved reporting), POST /templates/import/compose (compose YAML →
v2 config; known db images become managed databases, build: flagged in
warnings), POST /templates/deploy (ad-hoc graph deploy — the compose
import companion).

Surfaces: CLI gains templates plan/import-compose/deploy-graph plus
--name/--var on deploy; 3 new MCP tools (88 total); OpenAPI + generated
frontend types; TemplatesPage shows stack members, deploys graphs without
a name field, renders the created resource list, and ships an
Import Compose modal feeding the template editor.

Seeded: WordPress + MySQL and n8n + PostgreSQL graph templates.

Partial-failure cleanup: resources created by a failed graph deploy are
removed (rows, containers, volumes).

Verified live: wordpress-stack deploy created a managed MySQL attached to
the project network as `db`; an inline pg+redis+nginx graph deployed with
DATABASE_URL=postgresql://app:<gen>@pg:5432/shop resolvable in-container.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/api/databases.go

@@ -3,6 +3,7 @@ package api
 import (
 	"archive/tar"
 	"containr/internal/database/sqlcdb"
+	"containr/internal/deployment"
 	"containr/internal/docker"
 	"containr/internal/secrets"
 	"context"
@@ -331,6 +332,11 @@ type managedDatabaseCreateRequest struct {
 	Region           string
 	PublicPort       bool
 	RuntimeVariables map[string]string
+	// ProjectID + NetworkAlias attach the container to a project network
+	// under Alias — set by graph-template deploys so sibling services can
+	// resolve the database by name.
+	ProjectID    string
+	NetworkAlias string
 }
 
 func (h *DatabaseHandler) createManagedDatabase(ctx context.Context, userID string, req managedDatabaseCreateRequest) (databaseID string, name string, dbType string, err error) {
@@ -398,10 +404,17 @@ func (h *DatabaseHandler) createManagedDatabaseAndProvision(ctx context.Context,
 		return "", err
 	}
 
-	go h.provisionDatabaseWithVariables(databaseID, name, dbType, req.RuntimeVariables)
+	go h.provisionDatabaseWithVariables(databaseID, name, dbType, req.RuntimeVariables, dbNetworkAttach{ProjectID: req.ProjectID, Alias: req.NetworkAlias})
 	return databaseID, nil
 }
 
+// dbNetworkAttach carries the optional project-network membership for a
+// managed database provisioned by a graph template.
+type dbNetworkAttach struct {
+	ProjectID string
+	Alias     string
+}
+
 // UpdateDatabase updates a database service
 func (h *DatabaseHandler) UpdateDatabase(c *gin.Context) {
 	userID, ok := requireAuthenticatedUserID(c)
@@ -1350,7 +1363,7 @@ type databaseRuntimePlan struct {
 }
 
 func (h *DatabaseHandler) provisionDatabase(databaseID, databaseName, dbType string) {
-	h.provisionDatabaseWithVariables(databaseID, databaseName, dbType, nil)
+	h.provisionDatabaseWithVariables(databaseID, databaseName, dbType, nil, dbNetworkAttach{})
 }
 
 // reprovisionManagedDatabase recreates a managed container so changed
@@ -1364,7 +1377,7 @@ func (h *DatabaseHandler) reprovisionManagedDatabase(databaseID, databaseName, d
 	h.provisionDatabase(databaseID, databaseName, dbType)
 }
 
-func (h *DatabaseHandler) provisionDatabaseWithVariables(databaseID, databaseName, dbType string, runtimeVariables map[string]string) {
+func (h *DatabaseHandler) provisionDatabaseWithVariables(databaseID, databaseName, dbType string, runtimeVariables map[string]string, attach dbNetworkAttach) {
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
 	defer cancel()
 
@@ -1373,7 +1386,7 @@ func (h *DatabaseHandler) provisionDatabaseWithVariables(databaseID, databaseNam
 		return
 	}
 
-	connectionURL, err := h.provisionDatabaseRuntime(ctx, databaseID, databaseName, dbType, runtimeVariables)
+	connectionURL, err := h.provisionDatabaseRuntime(ctx, databaseID, databaseName, dbType, runtimeVariables, attach)
 	if err != nil {
 		log.Printf("containr: managed database %s (%s) provisioning failed: %v", databaseID, dbType, err)
 		_ = h.setDatabaseStatusAndConnection(databaseID, "error", sql.NullString{})
@@ -1395,7 +1408,7 @@ func (h *DatabaseHandler) setDatabaseStatusAndConnection(databaseID, status stri
 	})
 }
 
-func (h *DatabaseHandler) provisionDatabaseRuntime(ctx context.Context, databaseID, databaseName, dbType string, runtimeVariables map[string]string) (string, error) {
+func (h *DatabaseHandler) provisionDatabaseRuntime(ctx context.Context, databaseID, databaseName, dbType string, runtimeVariables map[string]string, attach dbNetworkAttach) (string, error) {
 	plan, err := buildDatabaseRuntimePlan(dbType, databaseName, runtimeVariables)
 	if err != nil {
 		return "", err
@@ -1483,6 +1496,17 @@ func (h *DatabaseHandler) provisionDatabaseRuntime(ctx context.Context, database
 		return "", fmt.Errorf("failed to start container: %w", err)
 	}
 
+	// Graph-template deploys attach the database to the project network so
+	// sibling services resolve it by alias ({{service.<key>.host}}).
+	if attach.ProjectID != "" && attach.Alias != "" {
+		projectNet := deployment.ProjectNetworkName(attach.ProjectID)
+		if err := h.dockerClient.ConnectNetwork(ctx, projectNet, containerID, network.EndpointSettings{
+			Aliases: []string{attach.Alias},
+		}); err != nil {
+			log.Printf("containr: database %s attach to %s failed: %v", databaseID, projectNet, err)
+		}
+	}
+
 	hostPort, err := h.resolvePublishedHostPort(ctx, containerID, plan.Port)
 	if err != nil {
 		return "", err