Persist campaign/encounter selection + scroll position across reload

UI reset to top on every reload/code update. Now:
- selectedCampaignId persisted via localStorage
- selectedEncounterId persisted via localStorage
- scrollY saved (beforeunload + pagehide + visibilitychange + 2s interval
  for Android Chrome reliability)
- scroll restored after campaigns data loads (300ms delay for mobile render)

src/App.js

@@ -1,3 +1,4 @@
+//
 import React, { useState, useEffect, useRef, useMemo, createContext, useContext, useCallback } from 'react';
 import * as shared from '@ttrpg/shared';
 import { initializeApp, getAuth, signInAnonymously, onAuthStateChanged, signInWithCustomToken, getFirestore, where, orderBy, limit, offset, getStorage, getStorageMode } from './storage';
@@ -2261,7 +2262,10 @@ function EncounterManager({ campaignId, initialActiveEncounterId, campaignCharac
   const { data: campaignDoc } = useFirestoreDocument(campaignId ? getPath.campaign(campaignId) : null);
 
   const [encounters, setEncounters] = useState([]);
-  const [selectedEncounterId, setSelectedEncounterId] = useState(null);
+  const [selectedEncounterId, setSelectedEncounterId] = useState(() => {
+    try { return localStorage.getItem('ttrpg.selectedEncounter') || null; }
+    catch { return null; }
+  });
   const [showCreateModal, setShowCreateModal] = useState(false);
   const [showDeleteConfirm, setShowDeleteConfirm] = useState(false);
   const [itemToDelete, setItemToDelete] = useState(null);
@@ -2314,6 +2318,10 @@ function EncounterManager({ campaignId, initialActiveEncounterId, campaignCharac
 
   useEffect(() => {
     selectedEncounterIdRef.current = selectedEncounterId;
+    try {
+      if (selectedEncounterId) localStorage.setItem('ttrpg.selectedEncounter', selectedEncounterId);
+      else localStorage.removeItem('ttrpg.selectedEncounter');
+    } catch {}
   }, [selectedEncounterId]);
 
   useEffect(() => {
@@ -2636,11 +2644,53 @@ function AdminView({ userId }) {
 
   const [campaignsWithDetails, setCampaignsWithDetails] = useState([]);
   const [draggedCampaignId, setDraggedCampaignId] = useState(null);
-  const [selectedCampaignId, setSelectedCampaignId] = useState(null);
+  const [selectedCampaignId, setSelectedCampaignId] = useState(() => {
+    try { return localStorage.getItem('ttrpg.selectedCampaign') || null; }
+    catch { return null; }
+  });
   const encounterStartedRef = useRef(false);
   const encounterActiveRef = useRef(false);
   const manualSelectRef = useRef(false);
   const prevDisplayCampaignRef = useRef(null);
+  const scrollRestoredRef = useRef(false);
+
+  // Save scroll on unload + visibility change + interval.
+  useEffect(() => {
+    const onSave = () => {
+      try { localStorage.setItem('ttrpg.scrollY', String(window.scrollY)); } catch {}
+    };
+    window.addEventListener('beforeunload', onSave);
+    window.addEventListener('pagehide', onSave);
+    document.addEventListener('visibilitychange', onSave);
+    const interval = setInterval(onSave, 2000);
+    return () => {
+      window.removeEventListener('beforeunload', onSave);
+      window.removeEventListener('pagehide', onSave);
+      document.removeEventListener('visibilitychange', onSave);
+      clearInterval(interval);
+    };
+  }, []);
+
+  // Restore scroll once data loaded.
+  useEffect(() => {
+    if (scrollRestoredRef.current) return;
+    if (campaignsWithDetails.length === 0) return;
+    try {
+      const y = parseInt(localStorage.getItem('ttrpg.scrollY') || '0', 10);
+      if (y > 0) {
+        scrollRestoredRef.current = true;
+        setTimeout(() => window.scrollTo(0, y), 300);
+      }
+    } catch {}
+  }, [campaignsWithDetails]);
+
+  // Persist selections across reload.
+  useEffect(() => {
+    try {
+      if (selectedCampaignId) localStorage.setItem('ttrpg.selectedCampaign', selectedCampaignId);
+      else localStorage.removeItem('ttrpg.selectedCampaign');
+    } catch {}
+  }, [selectedCampaignId]);
 
   // External display change (replay/other DM) = clear manual override, allow follow.
   useEffect(() => {