初始提交：QQ 群入群验证机器人

基于 qqbotsdk-py 的入群验证：进群发按钮验证码、完成前禁言、
超时踢出（11253 时兜底长期禁言）、乱点他人按钮处罚、状态持久化
与重启恢复。38 个单元/集成测试。

tests/test_captcha.py

@@ -0,0 +1,70 @@
+"""验证码生成与编解码测试。"""
+
+import pytest
+
+from authbot import captcha
+
+
+def test_generate_basic_properties():
+    for _ in range(50):
+        cap = captcha.generate(4)
+        assert len(cap.options) == 4
+        assert len(set(cap.options)) == 4  # 选项互不重复
+        assert cap.answer in cap.options
+        assert all(v >= 0 for v in cap.options)
+        # 运算式与答案自洽
+        expected = cap.a + cap.b if cap.op == "+" else cap.a - cap.b if cap.op == "-" else cap.a * cap.b
+        assert expected == cap.answer
+        assert cap.op in ("+", "-", "×")
+
+
+def test_generate_option_count_variants():
+    for n in (2, 3, 5):
+        cap = captcha.generate(n)
+        assert len(cap.options) == n
+        assert len(set(cap.options)) == n
+
+
+def test_token_unique_per_captcha():
+    tokens = {captcha.generate().token for _ in range(100)}
+    assert len(tokens) == 100
+
+
+def test_parse_button_data_roundtrip():
+    token, value = "abc123", 42
+    encoded = captcha.encode_button_data(token, value)
+    assert captcha.parse_button_data(encoded) == (token, value)
+
+
+@pytest.mark.parametrize(
+    "data",
+    ["", "v|", "v|abc", "v|abc|x", "hello|abc|1", "cmd|abc|1", "v|abc|1|2"],
+)
+def test_parse_button_data_rejects_invalid(data):
+    assert captcha.parse_button_data(data) is None
+
+
+def test_keyboard_structure():
+    cap = captcha.generate(4)
+    kb = cap.keyboard()
+    rows = kb["content"]["rows"]
+    assert len(rows) == 2  # 每行 2 个按钮
+    flat = [btn for row in rows for btn in row["buttons"]]
+    assert len(flat) == 4
+    labels = {btn["render_data"]["label"] for btn in flat}
+    assert labels == {str(v) for v in cap.options}
+    for btn in flat:
+        token, value = captcha.parse_button_data(btn["action"]["data"])
+        assert token == cap.token
+        assert value in cap.options
+        assert btn["action"]["type"] == 1  # 回调按钮
+
+
+def test_markdown_templates():
+    cap = captcha.generate(4)
+    welcome = captcha.welcome_markdown(cap, 10)
+    assert "10 分钟" in welcome
+    assert cap.question in welcome
+    retry = captcha.retry_markdown(cap)
+    assert cap.question in retry
+    assert "换一题" in retry