fix(v0.5.0): pre-release polish from full-codebase review

- Plugin.cs: mark RetentionSweepRunning volatile so the ImGui thread
  reads the latest value without a stale register-cached copy
- EmoteCache.cs: reset State to Unloaded on exception so a later
  trigger can retry instead of being blocked by the early-out
- Settings.cs: switch the SaveAndClose / Discard buttons to Allman
  bracing for consistency with the rest of the file, and include the
  ItemSpacing in the Ko-fi-button right-edge calculation
- Privacy.cs: add a saved-policy hint above the manual retention
  Ctrl+Shift button so the existing Cleanup wording pattern is
  matched here too
- HellionStrings: drop seven unreferenced keys (Theme_Heading,
  Migration_Notification_*, Migration_Webinterface_Removed_*,
  AutoTellTabs_Migration_*) and their EN/DE values, add the new
  Retention_Help_SavedNote string

ChatTwo/EmoteCache.cs

@@ -105,6 +105,11 @@ public static class EmoteCache
         }
         catch (Exception ex)
         {
+            // Reset to Unloaded so a later trigger (e.g. the user reopening
+            // the Emotes tab after the network recovers) can retry. Without
+            // this the State stays on Loading and the early-out at the top
+            // of LoadData blocks every further attempt until plugin reload.
+            State = LoadingState.Unloaded;
             Plugin.Log.Error(ex, "BetterTTV cache wasn't initialized");
         }
     }