docs(user): update device and sync navigation for sidebar UI

The new-ui redesign replaced the top header with a sidebar and removed
the Settings pages.

- Replace all 'Settings → Devices' paths with the Devices page in the
  sidebar
- Conflicts are resolved from the book detail page's Sync Progress
  button or the Conflicts page (/conflicts); drop the nonexistent
  'Settings → Conflicts' path
- Queue status and unlinked-book references no longer invent per-device
  button paths that don't exist on the Devices page
- Reading history now points to the Progress page / book detail
- Export FAQ no longer references a Settings → Export flow that isn't
  in the UI

docs/user/sync-guide.md

@@ -87,13 +87,13 @@ For detailed device configuration instructions, see the appropriate setup guide:
 **Registration Process** (KOReader):
 
 1. Install the Bookhoard plugin and enter your server URL in KOReader
-2. Approve the pending registration in Bookhoard (**Settings → Devices**)
+2. Approve the pending registration on the Bookhoard **Devices** page (sidebar navigation)
 3. That's it — sync starts automatically once approved
 
 **Device Management**:
 
 ```
-Settings → Devices
+Devices page (sidebar navigation)
 ```
 
 You can:
@@ -128,7 +128,7 @@ Sometimes a book on your device can't be automatically matched to your library.
 ### Viewing Unlinked Books
 
 ```
-Settings → Devices → Select Device → View Unlinked Books
+Devices page → select device → unlinked books
 ```
 
 ### Resolving Unlinked Books
@@ -288,7 +288,7 @@ This ensures your highlights work across all devices, even with different page c
 
 **Solutions**:
 
-1. Check device is online: `Settings → Devices`
+1. Check device is online: Devices page (sidebar navigation)
 2. Verify sync is enabled for the device
 3. Check sync URL is correct
 4. Ensure device has network connection
@@ -322,7 +322,7 @@ This ensures your highlights work across all devices, even with different page c
 
 **Solutions**:
 
-1. Go to `Settings → Conflicts`
+1. Open the book's detail page and click **Sync Progress**, or go to the Conflicts page (`/conflicts`)
 2. Review both device progress
 3. Choose which device's progress to keep
 4. Or choose "Merge" (keeps furthest progress)
@@ -397,7 +397,7 @@ This ensures your highlights work across all devices, even with different page c
 **Manual Resolution**:
 
 ```
-Settings → Conflicts → Select conflict → Choose winner
+Book detail → Sync Progress → choose winner
 ```
 
 **Options**:
@@ -412,7 +412,7 @@ Settings → Conflicts → Select conflict → Choose winner
 **View Queue Status**:
 
 ```
-Settings → Devices → Select Device → View Queue
+Devices page → sync queue section
 ```
 
 **Queue Stats**:
@@ -440,7 +440,7 @@ Settings → Devices → Select Device → View Queue
 **View History**:
 
 ```
-Book → Reading History
+Progress page (sidebar navigation), or the book's detail page
 ```
 
 **Privacy**:
@@ -526,7 +526,7 @@ A: No, devices are tied to individual accounts for security.
 A: All sync data for that book is removed from the server.
 
 **Q: Can I export my reading data?**
-A: Yes! Settings → Export → Download sync data.
+A: Reading data isn't exportable from the UI yet — it's accessible via the API.
 
 **Q: Does sync work over the internet?**
 A: Yes, if your server is publicly accessible with HTTPS.