docs(user): update appearance/profile instructions for sidebar UI

- Theme switching lives in the sidebar's Appearance panel (palette
  icon): swatch list with a checkmark on the active theme, and the
  'Bookshelf' section below it for wood textures; on small screens the
  sidebar opens via the top-bar menu button
- Profile: account menu is the username accordion at the bottom of the
  sidebar (not top-right); save button is 'Save Changes'
- Remove Wood Light/Dark/Mahogany from the Available Themes list (they
  are bookshelf backgrounds, not color themes) and consolidate the
  Catppuccin variants

docs/user/themes.md

@@ -18,10 +18,12 @@ Bookhoard includes multiple color themes to suit your preferences:
 
 ### Changing Your Theme
 
-1. Click the theme icon (palette) in the header
-2. Select your preferred color theme
+1. In the sidebar, open the **Appearance** panel (palette icon, near the bottom)
+2. Pick a theme from the list — each option shows its color swatch, and your active theme is marked with a checkmark
 3. Your choice is saved automatically and synced across devices
 
+On small screens, open the sidebar with the menu button in the top bar first.
+
 ## Wood Paneling
 
 Wood paneling adds texture to your dashboard bookshelf background, giving it a classic bookshelf feel.
@@ -35,10 +37,10 @@ Wood paneling adds texture to your dashboard bookshelf background, giving it a c
 
 ### Applying Wood Paneling
 
-1. Click the theme icon (palette) in the header
-2. Scroll to "Bookshelf Background" section
-3. Select your preferred wood texture
-4. Texture is applied to dashboard bookshelf only
+1. In the sidebar, open the **Appearance** panel (palette icon, near the bottom)
+2. Scroll to the **Bookshelf** section below the theme list
+3. Select your preferred wood texture (each option shows a texture swatch; **None** is the default)
+4. Texture is applied to the dashboard bookshelf background
 
 **Note:** Wood paneling is a browser preference and is not synced across devices.