fix(tg): reviewer fixes — error handling, timeouts, db index

- commands.py: try/except TelegramBadRequest around all Bot API calls (#2);
  /new handles "topics limit" with user-friendly message (#4)
- start.py: isolate _check_and_prune_stale_topics with try/except Exception (#3)
- message.py: asyncio.timeout(30) around stream_message; handle TimeoutError (#6)
- db.py: add idx_chats_user_id index in init_db() (#7)
- settings.py: remove dead active_chat_id variable (#8)
- tests: add test_message.py (stream error/success); add 2 tests in test_commands.py
  (topics limit, /archive in General topic)

tests/adapter/telegram/test_message.py

@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+import importlib
+from types import SimpleNamespace
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+
+
+@pytest.fixture(autouse=True)
+def fresh_db(tmp_path, monkeypatch):
+    monkeypatch.setenv("DB_PATH", str(tmp_path / "test.db"))
+    import adapter.telegram.db as db_mod
+    importlib.reload(db_mod)
+    db_mod.init_db()
+    return db_mod
+
+
+def make_message(*, user_id=1, thread_id=42, chat_id=100):
+    m = SimpleNamespace()
+    m.from_user = SimpleNamespace(id=user_id, full_name="Alice")
+    m.message_thread_id = thread_id
+    m.chat = SimpleNamespace(id=chat_id)
+    m.text = "Hello"
+    m.photo = None
+    m.document = None
+    m.voice = None
+    m.video = None
+    m.sticker = None
+    m.answer = AsyncMock()
+    placeholder = MagicMock()
+    placeholder.edit_text = AsyncMock()
+    m.reply = AsyncMock(return_value=placeholder)
+    m.bot = MagicMock()
+    return m, placeholder
+
+
+def make_dispatcher(chunks=None, raise_exc=None):
+    """Build a mock EventDispatcher with configurable stream_message behaviour."""
+    async def _stream(*args, **kwargs):
+        if raise_exc is not None:
+            raise raise_exc
+        for chunk in (chunks or []):
+            yield chunk
+
+    platform = MagicMock()
+    platform.get_or_create_user = AsyncMock(
+        return_value=SimpleNamespace(user_id="uid-1")
+    )
+    platform.stream_message = _stream
+
+    dispatcher = MagicMock()
+    dispatcher._platform = platform
+    return dispatcher
+
+
+async def test_stream_exception_shows_error(fresh_db):
+    """When stream_message raises, the placeholder is updated with an error message."""
+    fresh_db.create_chat(1, 42, "Чат #1")
+    import adapter.telegram.handlers.message as mod
+    importlib.reload(mod)
+
+    msg, placeholder = make_message()
+    dispatcher = make_dispatcher(raise_exc=RuntimeError("boom"))
+
+    await mod.handle_topic_message(msg, dispatcher)
+
+    placeholder.edit_text.assert_called()
+    last_call_text = placeholder.edit_text.call_args[0][0]
+    assert "недоступен" in last_call_text or "ошибка" in last_call_text.lower()
+
+
+async def test_stream_success_edits_placeholder(fresh_db):
+    """When stream_message succeeds, the placeholder is updated with the response."""
+    fresh_db.create_chat(1, 42, "Чат #1")
+    import adapter.telegram.handlers.message as mod
+    importlib.reload(mod)
+
+    chunks = [SimpleNamespace(delta="Hello "), SimpleNamespace(delta="world")]
+    msg, placeholder = make_message()
+    dispatcher = make_dispatcher(chunks=chunks)
+
+    await mod.handle_topic_message(msg, dispatcher)
+
+    placeholder.edit_text.assert_called()
+    last_call_text = placeholder.edit_text.call_args[0][0]
+    assert "Hello world" in last_call_text