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/mcpserver/server.go

@@ -126,6 +126,9 @@ func init() {
 	register(spec{"containr_templates_list", "List templates", "GET", "/templates", nil, nil, false})
 	register(spec{"containr_templates_get", "Get a template definition", "GET", "/templates/{id}", []string{"id"}, nil, false})
 	register(spec{"containr_templates_deploy", "Deploy a template into a project. Args: id (template), project_id.", "POST", "/templates/{id}/deploy", []string{"id"}, []string{"project_id"}, false})
+	register(spec{"containr_templates_plan", "Dry-resolve a template: expanded expressions, service refs, missing variables. Args: id, variables (object).", "POST", "/templates/{id}/plan", []string{"id"}, nil, false})
+	register(spec{"containr_templates_import_compose", "Convert docker-compose YAML into a v2 template graph config. Args: compose_yaml.", "POST", "/templates/import/compose", nil, []string{"compose_yaml"}, false})
+	register(spec{"containr_templates_deploy_graph", "Deploy an ad-hoc service graph without a stored template. Args: project_id, config ({services:[...]}), variables, plan, region.", "POST", "/templates/deploy", nil, []string{"project_id", "config", "variables", "plan", "region"}, false})
 
 	// Notifications
 	register(spec{"containr_notifications_list", "List notifications", "GET", "/notifications", nil, nil, false})