extract shared brandingVars() helper to eliminate duplication

The { brandName, brandAccent, brandLogo, settingsUrl } object was built
identically 3 times in the /confirm handler. Extract a brandingVars()
helper so it is defined once and reused via spread.

Closes mailship-90c

src/server.ts

@@ -299,16 +299,22 @@ addRoute('post', '/notify/:id', async (req: Request, res: Response) => {
   }
 })
 
+// ── Branding helper ──────────────────────────────────────────────────────
+
+const brandingVars = () => ({
+  brandName: BRAND_NAME,
+  brandAccent: BRAND_ACCENT,
+  brandLogo: BRAND_LOGO,
+  settingsUrl: `${EVENT_VIEWER_URL}/settings/alerts`,
+})
+
 // Confirmation
 addRoute('get', '/confirm', async (req: Request, res: Response) => {
   if (typeof req.query.token !== 'string') {
     return res.send(
       await render('pages/confirm-error.html', {
         message: 'No confirmation token was provided. Please check the link in your email and try again.',
-        brandName: BRAND_NAME,
+        ...brandingVars(),
-        brandAccent: BRAND_ACCENT,
-        brandLogo: BRAND_LOGO,
-        settingsUrl: `${EVENT_VIEWER_URL}/settings/alerts`,
       })
     )
   }
@@ -317,10 +323,7 @@ addRoute('get', '/confirm', async (req: Request, res: Response) => {
     await confirmSubscriptionAction({ token: req.query.token })
 
     res.send(await render('pages/confirm-success.html', {
-      brandName: BRAND_NAME,
+      ...brandingVars(),
-      brandAccent: BRAND_ACCENT,
-      brandLogo: BRAND_LOGO,
-      settingsUrl: `${EVENT_VIEWER_URL}/settings/alerts`,
     }))
   } catch (error) {
     const isActionError = error instanceof ActionError
@@ -328,10 +331,7 @@ addRoute('get', '/confirm', async (req: Request, res: Response) => {
 
     res.send(await render('pages/confirm-error.html', {
       message,
-      brandName: BRAND_NAME,
+      ...brandingVars(),
-      brandAccent: BRAND_ACCENT,
-      brandLogo: BRAND_LOGO,
-      settingsUrl: `${EVENT_VIEWER_URL}/settings/alerts`,
     }))
 
     if (!isActionError) {