Settings display demo and login fix (#4884)

# Description of Changes
<img width="1569" height="980" alt="image"
src="https://github.com/user-attachments/assets/dca1c227-ed84-4393-97a1-e3ce6eb1620b"
/>

<img width="1596" height="935" alt="image"
src="https://github.com/user-attachments/assets/2003e1be-034a-4cbb-869e-6d5d912ab61d"
/>

<img width="1543" height="997" alt="image"
src="https://github.com/user-attachments/assets/fe0c4f4b-eeee-4db4-a041-e554f350255a"
/>


---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### Translations (if applicable)

- [ ] I ran
[`scripts/counter_translation.py`](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/docs/counter_translation.md)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

frontend/public/locales/en-GB/translation.json

@@ -3177,6 +3177,7 @@
     "rememberme": "Remember me",
     "invalid": "Invalid username or password.",
     "locked": "Your account has been locked.",
+    "sessionExpired": "Your session has expired. Please sign in again.",
     "signinTitle": "Please sign in",
     "ssoSignIn": "Login via Single Sign-on",
     "oAuth2AutoCreateDisabled": "OAUTH2 Auto-Create User Disabled",
@@ -3681,6 +3682,12 @@
       "saveSuccess": "Settings saved successfully",
       "save": "Save Changes",
       "restartRequired": "Restart Required",
+      "loginRequired": "Login mode must be enabled to modify admin settings",
+      "loginDisabled": {
+        "title": "Login Mode Required",
+        "message": "Login mode must be enabled to modify admin settings. Please set SECURITY_ENABLELOGIN=true in your environment or security.enableLogin: true in settings.yml, then restart the server.",
+        "readOnly": "The settings below show example values for reference. Enable login mode to view and edit actual configuration."
+      },
       "restart": {
         "title": "Restart Required",
         "message": "Settings have been saved successfully. A server restart is required for the changes to take effect.",
@@ -3751,6 +3758,12 @@
             "description": "Default producer for PDF metadata"
           }
         },
+        "logoStyle": {
+          "label": "Logo Style",
+          "description": "Choose between the modern minimalist logo or the classic S icon",
+          "classic": "Classic",
+          "modern": "Modern"
+        },
         "customPaths": {
           "label": "Custom Paths",
           "description": "Configure custom file system paths for pipeline processing and external tools",