feat(templates): git compose import, six stack seeds, empty-default vars (#63)

* feat(templates): git compose import, six stack seeds, empty-default vars

- POST /templates/import/git fetches a compose file from any git remote
  (clone URL, ssh, owner/repo via connected providers — private repos
  included), ref selects branch or commit. Path defaults through
  compose.yaml/yml then docker-compose.yml/yaml. Reuses the build-on-node
  checkout machinery; repo-relative paths are containment-checked.
- CLI `templates import-git <repo> [path] [--ref]`, MCP
  containr_templates_import_git, OpenAPI entry, and a paste/git toggle
  in the template import dialog.
- {{VAR:-}} with an empty default now resolves instead of reporting the
  var missing — matches shell :- semantics.
- SeedTemplates gains six official graph stacks — n8n (pg+redis+worker),
  Gitea, Nextcloud, Vaultwarden, Umami, Immich — wired with
  {{service.*}} refs and {{secret}} credentials; no hardcoded passwords.
- TestSeedTemplatesResolveCleanly parses, topo-sorts, validates, and
  resolves every seeded graph — catalog drift can't merge silently.
- templates/n8n.md compose block had invalid YAML (mixed depends_on
  list/map) — fixed so the documented stack actually parses.

Verified live: import/git on a dumb-HTTP repo returns the converted
graph (db image → managed postgresql), path/ref/traversal/unauth edges
return clean errors, tpl-n8n plan resolves with zero unresolved vars.

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

* ci: pre-pull compose-smoke images via gcr mirror

Anonymous Docker Hub pulls rate-limit shared CI egress IPs — the compose
boot smoke flaked on traefik:pull. postgres/traefik are library/* images
served by mirror.gcr.io without auth; compose reuses the retagged local
images, falling back to a normal pull when the mirror misses.

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

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

* ci: route docker.io through gcr mirror for compose smoke

Pull-time pre-pulls don't cover BuildKit's base-image metadata lookups
(node:22-alpine, nginx:alpine, golang:1.26-alpine all 429). Daemon-level
registry-mirrors covers pulls and resolution in one move.

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

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

* ci: mirror docker.io in buildx for image publish job

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

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

* ci: route smoke pulls/builds through mirror.gcr.io via compose overlay

daemon.json registry-mirrors isn't honored by the runner's containerd
image store. Qualify refs directly: ARG-parameterized Dockerfile FROMs
(defaults unchanged) plus a CI-only compose overlay that points image
pulls and build args at mirror.gcr.io.

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

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

---------

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

app/backend/internal/cli/commands/templates.go

@@ -194,6 +194,32 @@ var templatesImportComposeCmd = &cobra.Command{
 	},
 }
 
+var templatesImportGitCmd = &cobra.Command{
+	Use:   "import-git <repo> [path]",
+	Short: "Fetch a compose file from a git repo and convert it into a template graph config",
+	Long:  "repo accepts a clone URL, ssh remote, or owner/repo shorthand resolved via connected git providers (private repos included). path defaults to compose.yaml/yml or docker-compose.yml/yaml. --ref selects a branch or commit.",
+	Args:  cobra.RangeArgs(1, 2),
+	RunE: func(cmd *cobra.Command, args []string) error {
+		body := map[string]string{"repo": args[0]}
+		if len(args) > 1 {
+			body["path"] = args[1]
+		}
+		if v, _ := cmd.Flags().GetString("ref"); v != "" {
+			body["ref"] = v
+		}
+		c, err := client()
+		if err != nil {
+			return err
+		}
+		data, err := c.Do("POST", "/templates/import/git", body)
+		if err != nil {
+			return err
+		}
+		PrintRaw(data)
+		return nil
+	},
+}
+
 var templatesDeployGraphCmd = &cobra.Command{
 	Use:   "deploy-graph <project-id> <config.json|->",
 	Short: "Deploy an ad-hoc service graph (v2 config with services[]) without a stored template",
@@ -257,5 +283,6 @@ func init() {
 	templatesDeployCmd.Flags().StringArrayVar(&tplDeployVars, "var", nil, "Template variable override (KEY=VALUE, repeatable)")
 	templatesPlanCmd.Flags().StringArrayVar(&tplDeployVars, "var", nil, "Template variable override (KEY=VALUE, repeatable)")
 	templatesDeployGraphCmd.Flags().StringArrayVar(&tplDeployVars, "var", nil, "Template variable override (KEY=VALUE, repeatable)")
-	TemplatesCmd.AddCommand(templatesListCmd, templatesGetCmd, templatesCreateCmd, templatesDeleteCmd, templatesDeployCmd, templatesPlanCmd, templatesImportComposeCmd, templatesDeployGraphCmd)
+	templatesImportGitCmd.Flags().String("ref", "", "git branch or commit (default: remote HEAD)")
+	TemplatesCmd.AddCommand(templatesListCmd, templatesGetCmd, templatesCreateCmd, templatesDeleteCmd, templatesDeployCmd, templatesPlanCmd, templatesImportComposeCmd, templatesImportGitCmd, templatesDeployGraphCmd)
 }