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/components/shared/branded-auth-shell.tsx

@@ -1,27 +1,42 @@
-const BG_URL = 'https://s3.portnimara.com/images/Overhead_1_blur.png';
-const LOGO_URL =
+const DEFAULT_BG_URL = 'https://s3.portnimara.com/images/Overhead_1_blur.png';
+const DEFAULT_LOGO_URL =
   'https://s3.portnimara.com/images/Port%20Nimara%20New%20Logo-Circular%20Frame_250px.png';
 
+interface BrandedAuthShellProps {
+  children: React.ReactNode;
+  /** Per-port branding override resolved server-side by the page that
+   *  renders the shell. When omitted, falls back to the Port Nimara
+   *  defaults so single-tenant deployments remain unaffected. Pages
+   *  that know their portId at render time should pass the result of
+   *  `getPortBrandingConfig(portId)`. */
+  branding?: {
+    logoUrl?: string | null;
+    appName?: string | null;
+  };
+}
+
 /**
  * Branded shell shared by every auth/form surface - CRM login, portal login,
- * password set/reset/activate, forgot-password. Renders the blurred Port
- * Nimara overhead background, the circular logo, and a centered white card
- * that consumers populate with their own form/content.
+ * password set/reset/activate, forgot-password. Renders the blurred
+ * background, the logo, and a centered white card that consumers
+ * populate with their own form/content.
+ *
+ * Multi-tenant note (R2-H15): the per-port logoUrl from
+ * /admin/branding is rendered when the parent page passes a `branding`
+ * prop. The background image stays as the marina default for all
+ * deployments — admin-authored backgrounds aren't part of the v1
+ * branding surface.
  */
-export function BrandedAuthShell({ children }: { children: React.ReactNode }) {
+export function BrandedAuthShell({ children, branding }: BrandedAuthShellProps) {
+  const logoUrl = branding?.logoUrl || DEFAULT_LOGO_URL;
+  const altText = branding?.appName || 'Port Nimara';
   return (
     <div className="relative min-h-screen min-h-[100dvh] flex items-center justify-center px-4 py-8">
-      {/*
-        Full-viewport background layer - pinned to the visible viewport via
-        `fixed inset-0` so the marina image always reaches the actual screen
-        edges regardless of the iOS Safari URL bar showing/hiding. The shell's
-        layout layer above sits on top via z-index.
-      */}
       <div
         aria-hidden
         className="fixed inset-0 -z-10"
         style={{
-          backgroundImage: `url('${BG_URL}')`,
+          backgroundImage: `url('${DEFAULT_BG_URL}')`,
           backgroundSize: 'cover',
           backgroundPosition: 'center',
           backgroundColor: '#f2f2f2',
@@ -31,7 +46,7 @@ export function BrandedAuthShell({ children }: { children: React.ReactNode }) {
         <div className="bg-white rounded-lg shadow-lg p-8">
           <div className="flex justify-center mb-6">
             {/* eslint-disable-next-line @next/next/no-img-element */}
-            <img src={LOGO_URL} alt="Port Nimara" className="w-24 h-auto" />
+            <img src={logoUrl} alt={altText} className="w-24 h-auto" />
           </div>
           {children}
         </div>