fix: harden data integrity, connection stability, and memory management

Wrap all multi-write DB operations in atomic transactions (server/channel
creation, message+attachment linking, DM creation, friend acceptance,
cascading deletes) to prevent partial-write corruption.

Batch N+1 queries in WS ready payload into O(1) bulk fetches with
chunked inArray() to respect SQLite's variable limit.

Fix chat history regression where background WS messages bypassed
channel load by switching the guard from messages.has() to hasMore.has().

Add LRU channel eviction (20 cached, evict to 15) and per-channel
message cap (200) to bound client memory growth.

Shorten WS heartbeat from 30s to 15s for aggressive proxy/NAT
environments. Clear all user-scoped stores on logout to prevent
cross-session data leaks.

Extract LiveKit internal accessors into shared livekitInternals utility.

packages/web/src/stores/chatStore.ts

@@ -5,6 +5,10 @@ import { wsSend } from '../hooks/useWebSocket';
 import { isDmChannel, useServerStore } from './serverStore';
 import { useAuthStore } from './authStore';
 
+const MAX_MESSAGES_PER_CHANNEL = 200;
+const MAX_CACHED_CHANNELS = 20;
+const EVICT_TO_CHANNELS = 15;
+
 interface TypingUser {
   userId: string;
   username: string;
@@ -27,6 +31,7 @@ interface ChatState {
   readStates: Map<string, string>;
   unreadChannels: Set<string>;
   realtimeMessageEvents: RealtimeMessageEvent[];
+  channelAccessTimes: Map<string, number>;
   setCurrentChannel: (channelId: string | null) => void;
   setReplyTo: (message: MessageWithUser | null) => void;
   loadMessages: (channelId: string, force?: boolean) => Promise<void>;
@@ -64,14 +69,59 @@ export const useChatStore = create<ChatState>((set, get) => ({
   readStates: new Map(),
   unreadChannels: new Set(),
   realtimeMessageEvents: [],
+  channelAccessTimes: new Map(),
 
-  setCurrentChannel: (channelId) => set({ currentChannelId: channelId }),
+  setCurrentChannel: (channelId) => {
+    set((state) => {
+      const newAccessTimes = new Map(state.channelAccessTimes);
+      if (channelId) {
+        newAccessTimes.set(channelId, Date.now());
+      }
+
+      // Evict stale channels if we have too many cached
+      let newMessages = state.messages;
+      let newHasMore = state.hasMore;
+      if (state.messages.size > MAX_CACHED_CHANNELS) {
+        const entries = [...newAccessTimes.entries()]
+          .filter(([id]) => id !== channelId)
+          .sort((a, b) => a[1] - b[1]);
+        const toEvict = state.messages.size - EVICT_TO_CHANNELS;
+        const evictIds = new Set(entries.slice(0, toEvict).map(([id]) => id));
+        if (evictIds.size > 0) {
+          newMessages = new Map(state.messages);
+          newHasMore = new Map(state.hasMore);
+          for (const id of evictIds) {
+            newMessages.delete(id);
+            newHasMore.delete(id);
+            newAccessTimes.delete(id);
+          }
+        }
+      }
+
+      return {
+        currentChannelId: channelId,
+        channelAccessTimes: newAccessTimes,
+        messages: newMessages,
+        hasMore: newHasMore,
+      };
+    });
+  },
   setReplyTo: (message) => set({ replyTo: message }),
 
-  clearAllMessages: () => set({ messages: new Map(), hasMore: new Map() }),
+  clearAllMessages: () => set({
+    messages: new Map(),
+    hasMore: new Map(),
+    typingUsers: new Map(),
+    readStates: new Map(),
+    unreadChannels: new Set(),
+    realtimeMessageEvents: [],
+    channelAccessTimes: new Map(),
+    currentChannelId: null,
+    replyTo: null,
+  }),
 
   loadMessages: async (channelId: string, force?: boolean) => {
-    if (!force && get().messages.has(channelId)) return;
+    if (!force && get().hasMore.has(channelId)) return;
     set({ isLoading: true, loadError: null });
     try {
       const isDm = isDmChannel(channelId);
@@ -84,7 +134,9 @@ export const useChatStore = create<ChatState>((set, get) => ({
         newMessages.set(channelId, messages as MessageWithUser[]);
         const newHasMore = new Map(state.hasMore);
         newHasMore.set(channelId, messages.length >= 50);
-        return { messages: newMessages, hasMore: newHasMore, isLoading: false, loadError: null };
+        const newAccessTimes = new Map(state.channelAccessTimes);
+        newAccessTimes.set(channelId, Date.now());
+        return { messages: newMessages, hasMore: newHasMore, channelAccessTimes: newAccessTimes, isLoading: false, loadError: null };
       });
     } catch (err) {
       set({ isLoading: false, loadError: (err as Error).message || 'Failed to load messages' });
@@ -232,7 +284,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
         if (!m.id.startsWith('temp_') || m.userId !== message.userId) return true;
         return m.content !== message.content;
       });
-      newMessages.set(channelId, [...filtered, message]);
+      let updated = [...filtered, message];
+      // Cap per-channel messages to prevent memory growth
+      if (updated.length > MAX_MESSAGES_PER_CHANNEL) {
+        updated = updated.slice(updated.length - MAX_MESSAGES_PER_CHANNEL);
+      }
+      newMessages.set(channelId, updated);
       return { messages: newMessages };
     });
   },
@@ -248,7 +305,12 @@ export const useChatStore = create<ChatState>((set, get) => ({
         if (!m.id.startsWith('temp_') || m.userId !== message.userId) return true;
         return m.content !== message.content;
       });
-      newMessages.set(channelId, [...filtered, message]);
+      let updated = [...filtered, message];
+      // Cap per-channel messages to prevent memory growth
+      if (updated.length > MAX_MESSAGES_PER_CHANNEL) {
+        updated = updated.slice(updated.length - MAX_MESSAGES_PER_CHANNEL);
+      }
+      newMessages.set(channelId, updated);
       // Append to realtimeMessageEvents (capped at 50)
       const newEvents = [...state.realtimeMessageEvents, { channelId, message }];
       if (newEvents.length > 50) newEvents.splice(0, newEvents.length - 50);