feat(channel): Improve and Enrich Channel Implementation in Agent Service

**Background**

The basic channel functionality has been established in v2.0.6 (#1997), with support for Feishu and Discord channels. However, further improvements are needed, including:

- Add new channel support, initially planned for WeCom (企业微信) and DingTalk
- Improve existing implementations:
- `DiscordChannel`: add `list_tools` support to expose corresponding tools
- Feishu, DingTalk and other IM channels: support adding a channel by scanning a QR code instead of manually entering the app ID and secret key
- Integrate channel with scheduled tasks, enabling scheduled triggers to wake up an agent and complete corresponding tasks in the target channel

**Tasks**

- Add WeCom channel support
- Add DingTalk channel support
- `DiscordChannel`: implement `list_tools`
- QR code-based channel binding for IM channels (Feishu, DingTalk, etc.)
- Integrate channel with scheduled task mechanism

Start by locating the existing channel implementation layer (Discord and Feishu channels) and the channel registration/auth flow in the Agent Service. Next, inspect the IM channel binding path to add QR-code based onboarding and find where scheduled task triggers are dispatched to channels. Add WeCom and DingTalk as channel adapters in the same integration model, extend `DiscordChannel` with `list_tools`, and wire scheduled tasks to wake the target channel agent. The issue is done when these integrations are discoverable at runtime and scheduled triggers execute via the selected channel.

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