fix(ui): inject window.FRONTEND_TYPE from server + rename SHOP→STOREFRONT

Server now injects window.FRONTEND_TYPE in all base templates via
get_context_for_frontend(). Both log-config.js and dev-toolbar.js read
this instead of guessing from URL paths, fixing:
- UNKNOWN prefix on merchant pages
- Incorrect detection on custom domains/subdomains in prod

Also adds frontend_type to login page contexts (admin, merchant, store).

Renames all [SHOP] logger prefixes to [STOREFRONT] across 7 files
(storefront-layout.js + 6 storefront templates).

Adds 'merchant' and 'storefront' to log-config.js frontend detection,
log levels, and logger selection.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/shared/js/dev-toolbar.js

@@ -286,11 +286,11 @@
     }
 
     function detectFrontend() {
+        // Prefer server-injected value (set in base templates)
+        if (window.FRONTEND_TYPE) return window.FRONTEND_TYPE;
+
+        // Fallback for pages without base template (e.g., API docs)
         var path = window.location.pathname;
-        if (path.startsWith('/store/') || path === '/store') return 'store';
-        if (path.startsWith('/admin/') || path === '/admin') return 'admin';
-        if (path.indexOf('/merchants/') !== -1) return 'merchant';
-        if (path.indexOf('/storefront/') !== -1) return 'storefront';
         if (path.startsWith('/api/')) return 'api';
         return 'unknown';
     }