fix(audit): wire 6 missing email subject overrides (R2-H14)

Admin-editable subject overrides at /admin/email-templates were no-ops
for 6 of 8 templates — only portal_activation and portal_reset called
loadSubjectOverride. Added a shared resolveSubject() helper and wired
it into the missing senders:

- crm_invite + portal_invite_resend (crm-invite.service.ts)
- inquiry_client_confirmation (email worker via portId on job payload)
- inquiry_sales_notification (email worker via portId on job payload)
- residential_inquiry_client_confirmation (residential-inquiries route)
- residential_inquiry_sales_alert (residential-inquiries route)

The inquiry email worker payloads now carry portId + portName so the
worker can resolve the per-port override; producers in inquiry-
notifications.service.ts pass them through.

1175/1175 vitest passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/email/resolve-subject.ts

@@ -0,0 +1,34 @@
+/**
+ * Helper that turns a template key + per-port settings into a final
+ * subject line. Centralises the override-resolution + token-substitution
+ * pattern so every transactional email sender is one call away from
+ * honoring the admin's `email_template_<key>_subject` override.
+ *
+ * Wire-up (per send site):
+ *   const subject = await resolveSubject({
+ *     key: 'crm_invite',
+ *     portId,
+ *     fallback: result.subject,
+ *     tokens: { portName, recipientName: data.recipientName, ttlHours: 48 },
+ *   });
+ *
+ * The override is read from `system_settings.email_template_<key>_subject`.
+ * If unset / empty / non-string, the `fallback` is returned as-is.
+ */
+
+import { loadSubjectOverride, applySubjectTokens } from '@/lib/email/template-overrides';
+import type { TemplateKey } from '@/lib/email/template-catalog';
+
+export async function resolveSubject(args: {
+  key: TemplateKey;
+  /** Optional — when omitted (e.g. system-level emails with no port
+   *  context), only the fallback subject is returned. */
+  portId?: string | null;
+  fallback: string;
+  tokens?: Record<string, string | number | undefined>;
+}): Promise<string> {
+  if (!args.portId) return args.fallback;
+  const override = await loadSubjectOverride(args.portId, args.key);
+  if (!override) return args.fallback;
+  return args.tokens ? applySubjectTokens(override, args.tokens) : override;
+}