feat(tmpl): {{domain_name}} placeholder — materialize on diff/apply, parameterize on snapshot

Adds internal/tmpl with Materialize (template placeholder -> zone name) and
Parameterize (zone name -> placeholder, the inverse used by the
template-from-zone snapshot). service.resolve now materializes the template
against DomainRef.ZoneName before diffing, so one template can be reused
across domains. LoadDomainFull (source query + hand-edited sqlc output, since
sqlc is not installed) now also selects zone_name to populate it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwxdSt4reTm7Dj1oxRvpP3

internal/store/db/domains.sql.go

@@ -184,7 +184,7 @@ func (q *Queries) ListDomains(ctx context.Context, projectID uuid.UUID) ([]Domai
 }
 
 const loadDomainFull = `-- name: LoadDomainFull :one
-SELECT d.zone_id, a.provider, a.secret_enc, t.doc
+SELECT d.zone_id, d.zone_name, a.provider, a.secret_enc, t.doc
 FROM domains d
 JOIN provider_accounts a ON a.id = d.provider_account_id
 LEFT JOIN templates t ON t.id = d.template_id
@@ -198,6 +198,7 @@ type LoadDomainFullParams struct {
 
 type LoadDomainFullRow struct {
 	ZoneID    string           `json:"zone_id"`
+	ZoneName  string           `json:"zone_name"`
 	Provider  string           `json:"provider"`
 	SecretEnc string           `json:"secret_enc"`
 	Doc       *dto.TemplateDoc `json:"doc"`
@@ -208,6 +209,7 @@ func (q *Queries) LoadDomainFull(ctx context.Context, arg LoadDomainFullParams)
 	var i LoadDomainFullRow
 	err := row.Scan(
 		&i.ZoneID,
+		&i.ZoneName,
 		&i.Provider,
 		&i.SecretEnc,
 		&i.Doc,