refactor(qqbot): split qqbot.py into package & add QR scan-to-configure onboard flow

- Refactor gateway/platforms/qqbot.py into gateway/platforms/qqbot/ package:
  - adapter.py: core QQAdapter (unchanged logic, constants from shared module)
  - constants.py: shared constants (API URLs, timeouts, message types)
  - crypto.py: AES-256-GCM key generation and secret decryption
  - onboard.py: QR-code scan-to-configure API (create_bind_task, poll_bind_result)
  - utils.py: User-Agent builder, HTTP headers, config helpers
  - __init__.py: re-exports all public symbols for backward compatibility

- Add interactive QR-code setup flow in hermes_cli/gateway.py:
  - Terminal QR rendering via qrcode package (graceful fallback to URL)
  - Auto-refresh on QR expiry (up to 3 times)
  - AES-256-GCM encrypted credential exchange
  - DM security policy selection (pairing/allowlist/open)

- Update hermes_cli/setup.py to delegate to gateway's _setup_qqbot()
- Add qrcode>=7.4 dependency to pyproject.toml and requirements.txt

hermes_cli/config.py

@@ -44,7 +44,7 @@ _EXTRA_ENV_KEYS = frozenset({
     "WEIXIN_HOME_CHANNEL", "WEIXIN_HOME_CHANNEL_NAME", "WEIXIN_DM_POLICY", "WEIXIN_GROUP_POLICY",
     "WEIXIN_ALLOWED_USERS", "WEIXIN_GROUP_ALLOWED_USERS", "WEIXIN_ALLOW_ALL_USERS",
     "BLUEBUBBLES_SERVER_URL", "BLUEBUBBLES_PASSWORD",
-    "QQ_APP_ID", "QQ_CLIENT_SECRET", "QQ_HOME_CHANNEL", "QQ_HOME_CHANNEL_NAME",
+    "QQ_APP_ID", "QQ_CLIENT_SECRET", "QQBOT_HOME_CHANNEL", "QQBOT_HOME_CHANNEL_NAME",
     "QQ_ALLOWED_USERS", "QQ_GROUP_ALLOWED_USERS", "QQ_ALLOW_ALL_USERS", "QQ_MARKDOWN_SUPPORT",
     "QQ_STT_API_KEY", "QQ_STT_BASE_URL", "QQ_STT_MODEL",
     "TERMINAL_ENV", "TERMINAL_SSH_KEY", "TERMINAL_SSH_PORT",
@@ -1534,12 +1534,12 @@ OPTIONAL_ENV_VARS = {
         "prompt": "Allow All QQ Users",
         "category": "messaging",
     },
-    "QQ_HOME_CHANNEL": {
+    "QQBOT_HOME_CHANNEL": {
         "description": "Default QQ channel/group for cron delivery and notifications",
         "prompt": "QQ Home Channel",
         "category": "messaging",
     },
-    "QQ_HOME_CHANNEL_NAME": {
+    "QQBOT_HOME_CHANNEL_NAME": {
         "description": "Display name for the QQ home channel",
         "prompt": "QQ Home Channel Name",
         "category": "messaging",