feat: add QQ Bot platform adapter (Official API v2)

Add full QQ Bot integration via the Official QQ Bot API (v2):
- WebSocket gateway for inbound events (C2C, group, guild, DM)
- REST API for outbound text/markdown/media messages
- Voice transcription (Tencent ASR + configurable STT provider)
- Attachment processing (images, voice, files)
- User authorization (allowlist + allow-all + DM pairing)

Integration points:
- gateway: Platform.QQ enum, adapter factory, allowlist maps
- CLI: setup wizard, gateway config, status display, tools config
- tools: send_message cross-platform routing, toolsets
- cron: delivery platform support
- docs: QQ Bot setup guide

cron/scheduler.py

@@ -44,7 +44,7 @@ logger = logging.getLogger(__name__)
 _KNOWN_DELIVERY_PLATFORMS = frozenset({
     "telegram", "discord", "slack", "whatsapp", "signal",
     "matrix", "mattermost", "homeassistant", "dingtalk", "feishu",
-    "wecom", "wecom_callback", "weixin", "sms", "email", "webhook", "bluebubbles",
+    "wecom", "wecom_callback", "weixin", "sms", "email", "webhook", "bluebubbles", "qq",
 })
 
 from cron.jobs import get_due_jobs, mark_job_run, save_job_output, advance_next_run
@@ -254,6 +254,7 @@ def _deliver_result(job: dict, content: str, adapters=None, loop=None) -> Option
         "email": Platform.EMAIL,
         "sms": Platform.SMS,
         "bluebubbles": Platform.BLUEBUBBLES,
+        "qq": Platform.QQ,
     }
     platform = platform_map.get(platform_name.lower())
     if not platform: