fix(frontend): share one theme setting between the login page and console

The login page stored its theme under thecloud-theme while the console read floci-theme, so a choice made at sign-in was lost. Both now use floci-theme (falling back to the old key once), and useTheme tolerates unavailable storage.

packages/api/public/login.js

@@ -1,4 +1,6 @@
 (() => {
+    // Shared with the console (useTheme.ts, index.html) so one choice applies everywhere.
+    const THEME_KEY = 'floci-theme';
     const root = document.documentElement;
     const buttons = document.querySelectorAll('.tg button');
     const reducedMotion = matchMedia('(prefers-reduced-motion: reduce)').matches;
@@ -6,7 +8,7 @@
     function setTheme(theme) {
         root.setAttribute('data-theme', theme);
         try {
-            localStorage.setItem('thecloud-theme', theme);
+            localStorage.setItem(THEME_KEY, theme);
         } catch (ignored) {
             // Theme persistence is optional when browser storage is unavailable.
         }
@@ -15,7 +17,7 @@
 
     let initialTheme = matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
     try {
-        const savedTheme = localStorage.getItem('thecloud-theme');
+        const savedTheme = localStorage.getItem(THEME_KEY) ?? localStorage.getItem('thecloud-theme');
         if (savedTheme === 'dark' || savedTheme === 'light' || savedTheme === 'cyber') {
             initialTheme = savedTheme;
         }