fix: preserve theme preference on logout (addresses #318)

- Theme now persists when user logs out and logs back in
- Added documentation for BACKEND_HOST environment variable (addresses #321)
- Users can now bind to localhost only for reverse proxy setups
- Improved documentation for network configuration options

docs/CONFIGURATION.md

@@ -116,11 +116,16 @@ For backwards compatibility, some settings can be overridden via environment var
 1. **Authentication variables (from .env)** - Always highest priority
    - `PULSE_AUTH_USER`, `PULSE_AUTH_PASS`, `API_TOKEN`
 
-2. **System settings (from system.json)** - Normal priority
+2. **Network binding variables** - For reverse proxy setups
+   - `BACKEND_HOST` - IP address to bind to (default: `0.0.0.0`)
+     - Set to `127.0.0.1` or `localhost` to only listen on localhost (for reverse proxy)
+   - `FRONTEND_PORT` - Port to listen on (default: `7655`)
+
+3. **System settings (from system.json)** - Normal priority
    - If system.json exists, it takes precedence
    - If missing, environment variables are checked
 
-3. **Legacy environment variables** - Lowest priority (deprecated)
+4. **Legacy environment variables** - Lowest priority (deprecated)
    - `POLLING_INTERVAL` - Only used if system.json doesn't exist
    - `CONNECTION_TIMEOUT` - Can override system.json value
    - `ALLOWED_ORIGINS` - Can override system.json value

frontend-modern/src/App.tsx

@@ -182,10 +182,15 @@ function App() {
       console.error('Logout error:', error);
     }
     
-    // Clear all local storage EXCEPT a flag indicating this is a logout
+    // Clear all local storage EXCEPT theme preference and logout flag
+    const currentTheme = localStorage.getItem('theme');
     localStorage.clear();
     sessionStorage.clear();
     localStorage.setItem('just_logged_out', 'true');
+    // Preserve theme preference across logout
+    if (currentTheme) {
+      localStorage.setItem('theme', currentTheme);
+    }
     
     // Clear WebSocket connection
     if (wsStore()) {