fix(invoices): detect catalog drafts from fees

[endenis]

Context

Follow-up to #6532 to address the remaining review feedback about identifying Product Catalog drafts.

Description

• Recognize Product Catalog drafts through contract-linked fees.
• Keep the billing-segment check for drafts without fees.
• Add regression coverage for both cases.

[lago-claude-ai-agent]

Automated pre-review (advisory, not a required check) — verdict: HOLD · CI green

HOLD: fee-only product-catalog drafts are not handled safely end to end.

• RefreshDraftAndFinalizeService#recurring_invoice? still recognizes catalog invoices only through billing segments, so a fee-only draft with keep_anchor will incorrectly move its issuing date at finalization. Use the same contract-fee fallback and add a finalization regression spec.
• The new no-segments spec stubs the computation that production runs. The real catalog path deletes the existing fee and recomputes from an empty segment collection, producing a zero-value invoice. Cover the real result and preserve or rebuild the fee instead of only asserting service dispatch.