fix(bot): add missing sender_name param in Slack and Email channels (#3104)

Commit 4d34025 added the required `sender_name` parameter to
`BaseChannel._handle_message()` and updated `feishu.py`, but
`slack.py` and `email.py` were not updated in the same change.

This caused a `TypeError` on every inbound message in both channels.
Because Slack SDK swallows exceptions in asyncio listener callbacks,
the error was silent — the bot received events, added emoji reactions,
but never called the LLM or sent any reply.

Fix: pass `sender_name=sender_id` in SlackChannel and
`sender_name=sender` in EmailChannel.

Co-authored-by: scott.kim <scott@ScottMacBookPro.local>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 3 people

bot/vikingbot/channels/email.py

@@ -89,6 +89,7 @@ async def start(self) -> None:
 
                     await self._handle_message(
                         sender_id=sender,
+                        sender_name=sender,
                         chat_id=sender,
                         content=item["content"],
                         metadata=item.get("metadata", {}),

bot/vikingbot/channels/slack.py

@@ -167,6 +167,7 @@ async def _on_socket_request(
 
         await self._handle_message(
             sender_id=sender_id,
+            sender_name=sender_id,
             chat_id=chat_id,
             content=text,
             metadata={