fix: unify theme system - fix theme switching persistence

- Unified localStorage key to 'theme-preference' across all components
- Fixed header.tsx using wrong localStorage key ('theme' instead of 'theme-preference')
- Added localStorage hybrid persistence for instant theme changes
- Removed router.refresh() which was causing stale data revert
- Replaced Blue theme with Sepia
- Consolidated auth() calls to prevent race conditions
- Updated UserSettingsData types to include all themes

keep-notes/app/actions/user-settings.ts

@@ -0,0 +1,71 @@
+'use server'
+
+import { auth } from '@/auth'
+import { prisma } from '@/lib/prisma'
+import { revalidatePath } from 'next/cache'
+
+export type UserSettingsData = {
+  theme?: 'light' | 'dark' | 'auto' | 'sepia' | 'midnight'
+}
+
+/**
+ * Update user settings (theme, etc.)
+ */
+export async function updateUserSettings(settings: UserSettingsData) {
+  console.log('[updateUserSettings] Started with:', settings)
+  const session = await auth()
+
+  if (!session?.user?.id) {
+    console.error('[updateUserSettings] Unauthorized')
+    throw new Error('Unauthorized')
+  }
+
+  try {
+    const result = await prisma.user.update({
+      where: { id: session.user.id },
+      data: settings
+    })
+    console.log('[updateUserSettings] Success:', result)
+
+    revalidatePath('/', 'layout')
+
+    return { success: true }
+  } catch (error) {
+    console.error('Error updating user settings:', error)
+    throw new Error('Failed to update user settings')
+  }
+}
+
+/**
+ * Get user settings for current user
+ */
+export async function getUserSettings(userId?: string) {
+  let id = userId
+
+  if (!id) {
+    const session = await auth()
+    id = session?.user?.id
+  }
+
+  if (!id) {
+    return {
+      theme: 'light' as const
+    }
+  }
+
+  try {
+    const user = await prisma.user.findUnique({
+      where: { id },
+      select: { theme: true }
+    })
+
+    return {
+      theme: (user?.theme || 'light') as 'light' | 'dark' | 'auto'
+    }
+  } catch (error) {
+    console.error('Error getting user settings:', error)
+    return {
+      theme: 'light' as const
+    }
+  }
+}