feat(web): improve theme system clarity and fix login page theme selection

- Add descriptive labels to distinguish workspace vs user theme settings
- Fix login page theme selection not reflecting in dropdown
- Add ThemeInfoCard component explaining theme system
- Enhance ThemeSelect with effective theme indicators
- Improve UX by clarifying theme scope and priority

Resolves theme confusion between System > General > Theme and System > Basic > Edit > Theme

web/src/components/AuthFooter.tsx

@@ -1,6 +1,8 @@
 import { observer } from "mobx-react-lite";
+import { useState } from "react";
 import { cn } from "@/lib/utils";
 import { workspaceStore } from "@/store";
+import { loadTheme } from "@/utils/theme";
 import LocaleSelect from "./LocaleSelect";
 import ThemeSelect from "./ThemeSelect";
 
@@ -9,10 +11,22 @@ interface Props {
 }
 
 const AuthFooter = observer(({ className }: Props) => {
+  // Local state for login page theme since we can't persist to server
+  const [localTheme, setLocalTheme] = useState(workspaceStore.state.theme || "default");
+
+  const handleThemeChange = (theme: string) => {
+    // Update local state
+    setLocalTheme(theme);
+    // Update workspace store for immediate UI feedback
+    workspaceStore.state.setPartial({ theme });
+    // Apply theme to DOM
+    loadTheme(theme);
+  };
+
   return (
     <div className={cn("mt-4 flex flex-row items-center justify-center w-full gap-2", className)}>
       <LocaleSelect value={workspaceStore.state.locale} onChange={(locale) => workspaceStore.state.setPartial({ locale })} />
-      <ThemeSelect value={workspaceStore.state.theme} onValueChange={(theme) => workspaceStore.state.setPartial({ theme })} />
+      <ThemeSelect value={localTheme} onValueChange={handleThemeChange} />
     </div>
   );
 });

web/src/components/Settings/PreferencesSection.tsx

@@ -8,6 +8,7 @@ import { useTranslate } from "@/utils/i18n";
 import { convertVisibilityFromString, convertVisibilityToString } from "@/utils/memo";
 import LocaleSelect from "../LocaleSelect";
 import ThemeSelect from "../ThemeSelect";
+import ThemeInfoCard from "../ThemeInfoCard";
 import VisibilityIcon from "../VisibilityIcon";
 import WebhookSection from "./WebhookSection";
 
@@ -47,10 +48,15 @@ const PreferencesSection = observer(() => {
       </div>
 
       <div className="w-full flex flex-row justify-between items-center">
+        <div className="flex flex-col">
           <span>{t("setting.preference-section.theme")}</span>
+          <span className="text-xs text-muted-foreground">Your personal theme preference (overrides default)</span>
+        </div>
         <ThemeSelect value={setting.theme} onValueChange={handleThemeChange} />
       </div>
 
+      <ThemeInfoCard />
+
       <p className="font-medium text-muted-foreground">{t("setting.preference")}</p>
 
       <div className="w-full flex flex-row justify-between items-center">

web/src/components/Settings/WorkspaceSection.tsx

@@ -81,7 +81,10 @@ const WorkspaceSection = observer(() => {
       <Separator />
       <p className="font-medium text-foreground">{t("setting.system-section.title")}</p>
       <div className="w-full flex flex-row justify-between items-center">
-        <span>Theme</span>
+        <div className="flex flex-col">
+          <span>Default Theme</span>
+          <span className="text-xs text-muted-foreground">Sets the default theme for all users</span>
+        </div>
         <ThemeSelect
           value={workspaceGeneralSetting.theme || "default"}
           onValueChange={(value: string) => updatePartialSetting({ theme: value })}

web/src/components/ThemeInfoCard.tsx

@@ -0,0 +1,33 @@
+import { observer } from "mobx-react-lite";
+import { Info } from "lucide-react";
+import { userStore, workspaceStore } from "@/store";
+
+const ThemeInfoCard = observer(() => {
+  const userTheme = userStore.state.userGeneralSetting?.theme;
+  const workspaceTheme = workspaceStore.state.theme || "default";
+  const effectiveTheme = userTheme || workspaceTheme;
+
+  return (
+    <div className="border border-blue-200 bg-blue-50 dark:border-blue-800 dark:bg-blue-950 rounded-lg p-4">
+      <div className="flex items-start gap-3">
+        <Info className="w-5 h-5 text-blue-600 dark:text-blue-400 mt-0.5" />
+        <div className="space-y-2">
+          <h4 className="font-medium text-blue-900 dark:text-blue-100">Theme System</h4>
+          <div className="text-sm text-blue-800 dark:text-blue-200 space-y-1">
+            <p><strong>Current effective theme:</strong> {effectiveTheme}</p>
+            <p><strong>Workspace default:</strong> {workspaceTheme}</p>
+            {userTheme && (
+              <p><strong>Your preference:</strong> {userTheme}</p>
+            )}
+            <p className="text-xs mt-2">
+              Your personal theme preference overrides the workspace default. 
+              If you haven't set a personal preference, the workspace default is used.
+            </p>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+});
+
+export default ThemeInfoCard;

web/src/components/ThemeSelect.tsx

@@ -1,12 +1,14 @@
+import { observer } from "mobx-react-lite";
 import { Moon, Palette, Sun, Wallpaper } from "lucide-react";
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select";
-import { workspaceStore } from "@/store";
+import { workspaceStore, userStore } from "@/store";
 import { THEME_OPTIONS } from "@/utils/theme";
 
 interface ThemeSelectProps {
   value?: string;
   onValueChange?: (theme: string) => void;
   className?: string;
+  showEffectiveTheme?: boolean;
 }
 
 const THEME_ICONS: Record<string, JSX.Element> = {
@@ -16,9 +18,14 @@ const THEME_ICONS: Record<string, JSX.Element> = {
   whitewall: <Wallpaper className="w-4 h-4" />,
 };
 
-const ThemeSelect = ({ value, onValueChange, className }: ThemeSelectProps = {}) => {
+const ThemeSelect = observer(({ value, onValueChange, className, showEffectiveTheme = false }: ThemeSelectProps = {}) => {
   const currentTheme = value || workspaceStore.state.theme || "default";
   
+  // Calculate effective theme (user preference overrides workspace default)
+  const effectiveTheme = userStore.state.userGeneralSetting?.theme || workspaceStore.state.theme || "default";
+  
+  const displayTheme = showEffectiveTheme ? effectiveTheme : currentTheme;
+
   const handleThemeChange = (newTheme: Theme) => {
     if (onValueChange) {
       onValueChange(newTheme);
@@ -32,6 +39,9 @@ const ThemeSelect = ({ value, onValueChange, className }: ThemeSelectProps = {})
       <SelectTrigger className={className}>
         <div className="flex items-center gap-2">
           <SelectValue placeholder="Select theme" />
+          {showEffectiveTheme && effectiveTheme !== currentTheme && (
+            <span className="text-xs text-muted-foreground">(effective: {effectiveTheme})</span>
+          )}
         </div>
       </SelectTrigger>
       <SelectContent>
@@ -40,12 +50,15 @@ const ThemeSelect = ({ value, onValueChange, className }: ThemeSelectProps = {})
             <div className="flex items-center gap-2">
               {THEME_ICONS[option.value]}
               <span>{option.label}</span>
+              {showEffectiveTheme && option.value === effectiveTheme && (
+                <span className="text-xs text-green-600">✓</span>
+              )}
             </div>
           </SelectItem>
         ))}
       </SelectContent>
     </Select>
   );
-};
+});
 
 export default ThemeSelect;