feat(branding): wire per-port branding through every transactional email + auth shell (R2-H15)

Multi-tenant branding admin (/admin/branding) was saving 5 settings
that no code read — every port's emails shipped Port Nimara's logo
and color regardless. Now wired end-to-end:

New shared infrastructure:
- src/lib/email/shell.ts — renderShell() + brandingPrimaryColor()
  helpers; takes BrandingShell { logoUrl, primaryColor,
  emailHeaderHtml, emailFooterHtml }, falls back to Port Nimara
  defaults when null.
- src/lib/email/branding-resolver.ts — getBrandingShell(portId)
  thin wrapper over getPortBrandingConfig() that returns null on
  error / missing portId so senders never break on misconfig.

All 6 transactional templates refactored to use renderShell + the
shared accent color; portName now flows through every template
(crm-invite, portal activation/reset, both inquiries, both
residential templates, notification digest).

All 6 senders pass branding via getBrandingShell:
- portal-auth.service.ts (activation + reset)
- crm-invite.service.ts (resend path; create-invite has no portId
  yet so falls through to defaults)
- email worker (inquiry confirmation + sales notification)
- residential-inquiries route (client confirmation + sales alert)
- notification-digest.service.ts (digest)

BrandedAuthShell takes an optional `branding` prop with logoUrl +
appName (parent page server-fetches via getPortBrandingConfig).
Defaults to Port Nimara if omitted, so single-tenant deployments
are unaffected.

1175/1175 vitest passing.

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

src/lib/services/portal-auth.service.ts

@@ -9,6 +9,7 @@ import { env } from '@/lib/env';
 import { sendEmail } from '@/lib/email';
 import { activationEmail, resetEmail } from '@/lib/email/templates/portal-auth';
 import { loadSubjectOverride } from '@/lib/email/template-overrides';
+import { getBrandingShell } from '@/lib/email/branding-resolver';
 import {
   CodedError,
   ConflictError,
@@ -118,13 +119,14 @@ async function issueActivationToken(
 
   const link = `${env.APP_URL}/portal/activate?token=${encodeURIComponent(raw)}`;
   const subjectOverride = await loadSubjectOverride(portId, 'portal_activation');
+  const branding = await getBrandingShell(portId);
   const { subject, html, text } = activationEmail(
     {
       portName,
       link,
       ttlHours: ACTIVATION_TOKEN_TTL_HOURS,
     },
-    { subject: subjectOverride },
+    { subject: subjectOverride, branding },
   );
 
   try {
@@ -378,13 +380,14 @@ export async function requestPasswordReset(email: string): Promise<void> {
   const portName = port?.name ?? 'Port Nimara';
   const link = `${env.APP_URL}/portal/reset-password?token=${encodeURIComponent(raw)}`;
   const subjectOverride = await loadSubjectOverride(user.portId, 'portal_reset');
+  const branding = await getBrandingShell(user.portId);
   const { subject, html, text } = resetEmail(
     {
       portName,
       link,
       ttlMinutes: RESET_TOKEN_TTL_MINUTES,
     },
-    { subject: subjectOverride },
+    { subject: subjectOverride, branding },
   );
 
   try {