Add admin-configurable branding (colors, logo, favicon) and generic default fallbacks

Site Settings -> Branding now supports a Primary/Secondary/Accent brand color
system applied site-wide (buttons, nav, hover states, links) and to outgoing
email header/CTA colors, plus a favicon upload alongside the existing logo
upload, a live preview panel (website/email x desktop/mobile), and
logo-based color suggestions. The setup wizard's Branding step got the same
treatment. Fixes two related bugs found along the way: the setup wizard's
logo/favicon upload was missing its auth token, and a static favicon.ico in
Next's special app/ convention path was silently overriding the dynamic one.

Also replaces every "Hope Events"/"Hope Family Church" default (org name,
email subjects, WhatsApp messages, report metadata, API docs) with a neutral
"Cross Code" placeholder, and the optional legal settings (operator name, IO
details, website URL, effective date) with obviously-generic placeholders
instead of defaulting to real personal/organisational details -- since this
platform is deployed for multiple organisations. Adds SETTINGS.md documenting
every setting's default behaviour.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/routes/uploadRoutes.js

@@ -1,7 +1,7 @@
 const express = require('express');
 const router = express.Router();
 
-const { upload, uploadEventImage, uploadLogo, uploadLogoImage } = require('../controllers/uploadController');
+const { upload, uploadEventImage, uploadLogo, uploadLogoImage, uploadFavicon, uploadFaviconImage } = require('../controllers/uploadController');
 const { protect, supervisor, admin } = require('../middleware/authMiddleware');
 const prisma = require('../config/db');
 
@@ -17,11 +17,9 @@ router.post('/event-image', protect, supervisor, (req, res, next) => {
     });
 }, uploadEventImage);
 
-// @route POST /api/uploads/logo
-// @desc Upload site logo — admin, OR allowed during first-time setup (no users yet)
-// @access Admin or setup
-
-async function logoAccess(req, res, next) {
+// Shared access rule for branding assets (logo, favicon): admin, OR allowed
+// during first-time setup (no users yet).
+async function brandingAssetAccess(req, res, next) {
     try {
         const count = await prisma.user.count();
         if (count === 0) return next(); // first-time setup
@@ -31,11 +29,24 @@ async function logoAccess(req, res, next) {
     }
 }
 
-router.post('/logo', logoAccess, (req, res, next) => {
+// @route POST /api/uploads/logo
+// @desc Upload site logo — admin, OR allowed during first-time setup (no users yet)
+// @access Admin or setup
+router.post('/logo', brandingAssetAccess, (req, res, next) => {
     uploadLogo.single('image')(req, res, (err) => {
         if (err) req.multerError = err;
         next();
     });
 }, uploadLogoImage);
 
+// @route POST /api/uploads/favicon
+// @desc Upload site favicon — admin, OR allowed during first-time setup (no users yet)
+// @access Admin or setup
+router.post('/favicon', brandingAssetAccess, (req, res, next) => {
+    uploadFavicon.single('image')(req, res, (err) => {
+        if (err) req.multerError = err;
+        next();
+    });
+}, uploadFaviconImage);
+
 module.exports = router;