refactor(app): remove unsupported runtime and UI state

lib/screens/settings/in_settings/background_reliability.dart

@@ -2,12 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:revoltvpn/logic/app_colors.dart';
 import 'package:revoltvpn/logic/power_settings.dart';
 
-/// Keeping the tunnel alive is an OS concern, not an app one.
-///
-/// Android stops background services of apps that are not exempt from Doze, and
-/// removes the whole process group when its task is swiped away. There are
-/// exactly two sanctioned ways around that, both requiring one user tap, and
-/// neither can be enabled programmatically. This tile surfaces both.
+/// Android may restrict background work when battery optimisation is active.
+/// Surface the OS setting we can actually detect and request; do not promise
+/// reboot/Always-on restoration that the per-session runtime cannot guarantee.
 class BackgroundReliabilityTile extends StatefulWidget {
   const BackgroundReliabilityTile({super.key});
 
@@ -35,8 +32,6 @@ class _BackgroundReliabilityTileState extends State<BackgroundReliabilityTile>
 
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
-    // The exemption is granted in a system dialog, so the only reliable moment
-    // to re-read it is when we come back to the foreground.
     if (state == AppLifecycleState.resumed) _refresh();
   }
 
@@ -68,8 +63,8 @@ class _BackgroundReliabilityTileState extends State<BackgroundReliabilityTile>
             style: TextStyle(color: AppColors.textWhite, fontSize: 15),
           ),
           subtitle: Text(
-            'Android stops background apps to save power. Disabling battery '
-            'optimisation is what keeps the VPN running when the app is closed.',
+            'Android may restrict background work to save power. ReVolt only '
+            'shows the system control it can verify.',
             style: TextStyle(color: AppColors.textDim, fontSize: 12),
           ),
         ),
@@ -83,8 +78,8 @@ class _BackgroundReliabilityTileState extends State<BackgroundReliabilityTile>
                     ? 'Battery optimisation: checking…'
                     : exempt
                         ? 'Battery optimisation: disabled for Revolt VPN ✓'
-                        : 'Battery optimisation: still active — the system may '
-                            'stop the VPN in the background.',
+                        : 'Battery optimisation: active — Android may stop '
+                            'background VPN work.',
                 style: TextStyle(
                   color: exempt == true ? AppColors.accent : AppColors.textMuted,
                   fontSize: 12,