[web] Fix inconsistencies in storage volumes (#1109)

This fixes #1108, both the problems and the implemented solutions are
described there in depth.

Tested manually to check both problems are indeed fixed.

web/src/components/storage/ProposalPage.jsx

@@ -232,6 +232,7 @@ export default function ProposalPage() {
       <ProposalSettingsSection
         availableDevices={state.availableDevices}
         encryptionMethods={state.encryptionMethods}
+        volumeTemplates={state.volumeTemplates}
         settings={state.settings}
         onChange={changeSettings}
         isLoading={state.loading}

web/src/components/storage/ProposalSettingsSection.jsx

@@ -131,16 +131,14 @@ const SnapshotsField = ({
 }) => {
   const rootVolume = (settings.volumes || []).find((i) => i.mountPath === "/");
 
-  const initialChecked = rootVolume !== undefined && hasFS(rootVolume, "Btrfs") && rootVolume.snapshots;
-  const [isChecked, setIsChecked] = useState(initialChecked);
-
   // no root volume is probably some error or still loading
   if (rootVolume === undefined) {
     return <Skeleton width="25%" />;
   }
 
+  const isChecked = rootVolume !== undefined && hasFS(rootVolume, "Btrfs") && rootVolume.snapshots;
+
   const switchState = (_, checked) => {
-    setIsChecked(checked);
     onChange({ active: checked, settings });
   };