feat(core): clear saved chat and add message deletion scopes

backend:

- add message_hidden table for per-user message hiding

- support DELETE /messages/{id}?for_all=true|false

- implement delete-for-me vs delete-for-all logic by chat type/permissions

- add POST /chats/{chat_id}/clear and route saved chat deletion to clear

web:

- saved messages action changed from delete to clear

- message context menu now supports delete modal: for me / for everyone

- add local store helpers removeMessage/clearChatMessages

- include realtime stability improvements and app error boundary

web/src/components/ChatList.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from "react";
 import { createPortal } from "react-dom";
-import { deleteChat } from "../api/chats";
+import { clearChat, deleteChat } from "../api/chats";
 import { updateMyProfile } from "../api/users";
 import { useAuthStore } from "../store/authStore";
 import { useChatStore } from "../store/chatStore";
@@ -27,7 +27,11 @@ export function ChatList() {
   const [profileError, setProfileError] = useState<string | null>(null);
   const [profileSaving, setProfileSaving] = useState(false);
   const deleteModalChat = chats.find((chat) => chat.id === deleteModalChatId) ?? null;
-  const canDeleteForEveryone = Boolean(deleteModalChat && !deleteModalChat.is_saved && deleteModalChat.type === "group");
+  const canDeleteForEveryone = Boolean(
+    deleteModalChat &&
+    !deleteModalChat.is_saved &&
+    (deleteModalChat.type === "group" || deleteModalChat.type === "private")
+  );
 
   useEffect(() => {
     const timer = setTimeout(() => {
@@ -36,6 +40,20 @@ export function ChatList() {
     return () => clearTimeout(timer);
   }, [search, loadChats]);
 
+  useEffect(() => {
+    const onKeyDown = (event: KeyboardEvent) => {
+      if (event.key !== "Escape") {
+        return;
+      }
+      setCtxChatId(null);
+      setCtxPos(null);
+      setDeleteModalChatId(null);
+      setProfileOpen(false);
+    };
+    window.addEventListener("keydown", onKeyDown);
+    return () => window.removeEventListener("keydown", onKeyDown);
+  }, []);
+
   useEffect(() => {
     if (!me) {
       return;
@@ -141,7 +159,7 @@ export function ChatList() {
                 setDeleteForAll(false);
               }}
             >
-              Delete chat
+              {chats.find((c) => c.id === ctxChatId)?.is_saved ? "Clear chat" : "Delete chat"}
             </button>
           </div>,
           document.body
@@ -151,10 +169,15 @@ export function ChatList() {
       {deleteModalChatId ? (
         <div className="absolute inset-0 z-50 flex items-end justify-center bg-slate-950/55 p-3">
           <div className="w-full rounded-xl border border-slate-700/80 bg-slate-900 p-3">
-            <p className="mb-2 text-sm font-semibold">Delete chat: {deleteModalChat ? chatLabel(deleteModalChat) : "selected chat"}</p>
+            <p className="mb-2 text-sm font-semibold">
+              {deleteModalChat?.is_saved ? "Clear chat" : "Delete chat"}: {deleteModalChat ? chatLabel(deleteModalChat) : "selected chat"}
+            </p>
             {deleteModalChat?.type === "channel" ? (
               <p className="mb-3 text-xs text-slate-400">Channels are removed for all subscribers.</p>
             ) : null}
+            {deleteModalChat?.is_saved ? (
+              <p className="mb-3 text-xs text-slate-400">This will clear all messages in Saved Messages.</p>
+            ) : null}
             {canDeleteForEveryone ? (
               <label className="mb-3 flex items-center gap-2 text-sm">
                 <input checked={deleteForAll} onChange={(e) => setDeleteForAll(e.target.checked)} type="checkbox" />
@@ -165,6 +188,12 @@ export function ChatList() {
               <button
                 className="flex-1 rounded bg-red-500 px-3 py-2 text-sm font-semibold text-white"
                 onClick={async () => {
+                  if (deleteModalChat?.is_saved) {
+                    await clearChat(deleteModalChatId);
+                    useChatStore.getState().clearChatMessages(deleteModalChatId);
+                    setDeleteModalChatId(null);
+                    return;
+                  }
                   await deleteChat(deleteModalChatId, canDeleteForEveryone && deleteForAll);
                   await loadChats(search.trim() ? search : undefined);
                   if (activeChatId === deleteModalChatId) {
@@ -173,7 +202,7 @@ export function ChatList() {
                   setDeleteModalChatId(null);
                 }}
               >
-                Delete
+                {deleteModalChat?.is_saved ? "Clear" : "Delete"}
               </button>
               <button className="flex-1 rounded bg-slate-700 px-3 py-2 text-sm" onClick={() => setDeleteModalChatId(null)}>
                 Cancel