Add username search and improve chat creation UX

Backend user search:

- Added users search endpoint for @username lookup.

- Implemented repository/service/router support with bounded result limits.

Web chat creation:

- Added API client for /users/search.

- Added NewChatPanel for creating private chats via @username search.

- Added group/channel creation flow from sidebar.

UX refinement:

- Hide message composer when no chat is selected.

- Show explicit placeholder: 'Выберите чат, чтобы начать переписку'.

- Added tsbuildinfo ignore rule.

web/src/components/ChatList.tsx

@@ -1,4 +1,5 @@
 import { useChatStore } from "../store/chatStore";
+import { NewChatPanel } from "./NewChatPanel";
 
 export function ChatList() {
   const chats = useChatStore((s) => s.chats);
@@ -8,6 +9,7 @@ export function ChatList() {
   return (
     <aside className="w-full max-w-xs border-r border-slate-700 bg-panel">
       <div className="border-b border-slate-700 p-3 text-sm font-semibold">Chats</div>
+      <NewChatPanel />
       <div className="max-h-[calc(100vh-56px)] overflow-auto">
         {chats.map((chat) => (
           <button

web/src/components/NewChatPanel.tsx

@@ -0,0 +1,131 @@
+import { FormEvent, useMemo, useState } from "react";
+import { createChat, createPrivateChat, getChats } from "../api/chats";
+import { searchUsers } from "../api/users";
+import type { ChatType, UserSearchItem } from "../chat/types";
+import { useChatStore } from "../store/chatStore";
+
+type CreateMode = "private" | "group" | "channel";
+
+export function NewChatPanel() {
+  const [mode, setMode] = useState<CreateMode>("private");
+  const [query, setQuery] = useState("");
+  const [title, setTitle] = useState("");
+  const [results, setResults] = useState<UserSearchItem[]>([]);
+  const [loading, setLoading] = useState(false);
+  const [error, setError] = useState<string | null>(null);
+  const setActiveChatId = useChatStore((s) => s.setActiveChatId);
+
+  const normalizedQuery = useMemo(() => query.trim(), [query]);
+
+  async function handleSearch(value: string) {
+    setQuery(value);
+    setError(null);
+    if (value.trim().replace("@", "").length < 2) {
+      setResults([]);
+      return;
+    }
+    try {
+      const users = await searchUsers(value);
+      setResults(users);
+    } catch {
+      setError("Search failed");
+    }
+  }
+
+  async function refreshChatsAndSelectLast() {
+    const chats = await getChats();
+    useChatStore.setState({ chats });
+    if (chats[0]) {
+      setActiveChatId(chats[0].id);
+    }
+  }
+
+  async function createPrivate(userId: number) {
+    setLoading(true);
+    setError(null);
+    try {
+      await createPrivateChat(userId);
+      await refreshChatsAndSelectLast();
+      setQuery("");
+      setResults([]);
+    } catch {
+      setError("Failed to create private chat");
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  async function createByType(event: FormEvent) {
+    event.preventDefault();
+    if (mode === "private") {
+      return;
+    }
+    if (!title.trim()) {
+      setError("Title is required");
+      return;
+    }
+    setLoading(true);
+    setError(null);
+    try {
+      await createChat(mode as ChatType, title.trim(), []);
+      await refreshChatsAndSelectLast();
+      setTitle("");
+    } catch {
+      setError("Failed to create chat");
+    } finally {
+      setLoading(false);
+    }
+  }
+
+  return (
+    <div className="border-b border-slate-700 p-3">
+      <div className="mb-2 flex gap-2 text-xs">
+        <button className={`rounded px-2 py-1 ${mode === "private" ? "bg-accent text-black" : "bg-slate-700"}`} onClick={() => setMode("private")}>
+          Private
+        </button>
+        <button className={`rounded px-2 py-1 ${mode === "group" ? "bg-accent text-black" : "bg-slate-700"}`} onClick={() => setMode("group")}>
+          Group
+        </button>
+        <button className={`rounded px-2 py-1 ${mode === "channel" ? "bg-accent text-black" : "bg-slate-700"}`} onClick={() => setMode("channel")}>
+          Channel
+        </button>
+      </div>
+
+      {mode === "private" ? (
+        <div className="space-y-2">
+          <input
+            className="w-full rounded bg-slate-800 px-2 py-1 text-sm"
+            placeholder="@username"
+            value={query}
+            onChange={(e) => void handleSearch(e.target.value)}
+          />
+          <div className="max-h-32 overflow-auto">
+            {results.map((user) => (
+              <button
+                className="mb-1 block w-full rounded bg-slate-800 px-2 py-1 text-left text-sm hover:bg-slate-700"
+                key={user.id}
+                onClick={() => void createPrivate(user.id)}
+              >
+                @{user.username}
+              </button>
+            ))}
+            {normalizedQuery && results.length === 0 ? <p className="text-xs text-slate-400">No users</p> : null}
+          </div>
+        </div>
+      ) : (
+        <form className="space-y-2" onSubmit={(e) => void createByType(e)}>
+          <input
+            className="w-full rounded bg-slate-800 px-2 py-1 text-sm"
+            placeholder={mode === "group" ? "Group title" : "Channel title"}
+            value={title}
+            onChange={(e) => setTitle(e.target.value)}
+          />
+          <button className="w-full rounded bg-slate-700 px-2 py-1 text-sm hover:bg-slate-600" disabled={loading} type="submit">
+            Create {mode}
+          </button>
+        </form>
+      )}
+      {error ? <p className="mt-2 text-xs text-red-400">{error}</p> : null}
+    </div>
+  );
+}