Add Fastworkload custom domain template

[erikgaas]

Description

Adds the Fastworkload custom-domain template. It creates a wildcard ingress
CNAME, delegates ACME DNS-01 validation to Fastworkload, and adds a scoped TXT
record for domain ownership verification.

Type of change

Please mark options that are relevant.

• New template
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Template functionality checked using Online Editor
• Template file name follows the required providerId.serviceId.json pattern
• Resource URL in logoUrl is publicly accessible
• Template validates against the repository JSON schema
• Online Editor output matches the submitted template exactly
• Domain Connect signing key is published at _dck1.domainconnect.fastworkload.com

Checklist of common problems

• providerId is a domain controlled by the provider
• serviceId describes the service
• version is set
• logoUrl uses HTTPS and returns an SVG image
• syncPubKeyDomain is configured for synchronous flow signing
• syncRedirectDomain points to the Fastworkload console
• Record hosts are relative to the user-selected host
• Template variables are used for per-domain challenge and verification values
• No records are intended for independent modification; all three are required for routing, TLS, or ownership verification

Online Editor test results

The editor applied the template to example.com/apps and produced:

• *.apps.example.com CNAME ingress.fastworkload.com
• _acme-challenge.apps.example.com CNAME test-domain.acme.fastworkload.com
• _fastworkload.apps.example.com TXT fw-domain-verification=test-token-123456789

Editor test link(s):

Test fastworkload.com/custom-domain with example.com/apps