feat(theme): per-theme brand logos (VNClagoon wordmark ↔ SRC mark)

Add optional logoLightUrl/logoDarkUrl to InstalledTheme + resolveThemeLogo()
helper; set logos on vnclagoon + src themes; login page and nav-rail prefer the
active theme's logo, falling back to the global config logo. So switching theme
switches the whole brand. 0 type errors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

components/layout/navigation-rail.tsx

@@ -7,6 +7,7 @@ import { AccountSwitcher } from "./account-switcher";
 import { icons as lucideIcons, type LucideIcon } from "lucide-react";
 import { useConfig } from "@/hooks/use-config";
 import { useThemeStore } from "@/stores/theme-store";
+import { resolveThemeLogo } from "@/lib/theme-logo";
 import { usePathname, Link, useRouter } from "@/i18n/navigation";
 import { useTranslations } from "next-intl";
 import { useCalendarStore } from "@/stores/calendar-store";
@@ -190,6 +191,8 @@ export function NavigationRail({
   const router = useRouter();
   const { appLogoLightUrl, appLogoDarkUrl } = useConfig();
   const resolvedTheme = useThemeStore((s) => s.resolvedTheme);
+  const activeThemeId = useThemeStore((s) => s.activeThemeId);
+  const installedThemes = useThemeStore((s) => s.installedThemes);
   const { supportsCalendar } = useCalendarStore();
   const { mailboxes } = useEmailStore();
   const client = useAuthStore((s) => s.client);
@@ -462,7 +465,7 @@ export function NavigationRail({
       )}
     >
       {(() => {
-        const logoUrl = withBasePath(resolvedTheme === 'dark' ? (appLogoDarkUrl || appLogoLightUrl) : (appLogoLightUrl || appLogoDarkUrl));
+        const logoUrl = withBasePath(resolveThemeLogo(installedThemes, activeThemeId, resolvedTheme === 'dark', appLogoLightUrl, appLogoDarkUrl));
         return logoUrl ? (
           <div className="flex items-center justify-center py-3 px-1">
             <img