fix: 修复 Twitch 集成 - 降级到 twitchio 2.x

- 从 twitchio 3.x 降级到 2.10.0 (IRC-based)
  - 3.x 使用 EventSub API 需要更复杂的配置
  - 2.x 使用 IRC 方式更简单可靠
- 简化 Twitch 配置，只需要 Token 和频道名
- 移除 client_id, client_secret, bot_id 要求
- 更新 .env.example 配置说明

backend/app/twitch_service.py

@@ -0,0 +1,112 @@
+"""
+Twitch service for connecting to Twitch chat and handling events.
+Integrates with the game engine to process chat commands and bits.
+
+Compatible with twitchio 2.x (IRC-based)
+"""
+
+import os
+import logging
+from typing import TYPE_CHECKING
+
+from twitchio.ext import commands
+
+if TYPE_CHECKING:
+    from .engine import GameEngine
+
+logger = logging.getLogger(__name__)
+
+
+class TwitchBot(commands.Bot):
+    """
+    Twitch bot that listens to chat messages and bits events.
+    Forwards them to the game engine for processing.
+
+    Compatible with twitchio 2.x API (IRC-based).
+    """
+
+    def __init__(self, game_engine: "GameEngine"):
+        # Initialize bot with environment variables
+        self._token = os.getenv("TWITCH_TOKEN")
+        self._channel = os.getenv("TWITCH_CHANNEL_NAME")
+        prefix = os.getenv("TWITCH_COMMAND_PREFIX", "!")
+
+        if not self._token:
+            raise ValueError("TWITCH_TOKEN environment variable is required")
+        if not self._channel:
+            raise ValueError("TWITCH_CHANNEL_NAME environment variable is required")
+
+        # Store game engine reference
+        self._game_engine = game_engine
+
+        # Initialize the bot (twitchio 2.x API - IRC based)
+        super().__init__(
+            token=self._token,
+            prefix=prefix,
+            initial_channels=[self._channel]
+        )
+
+        logger.info(f"TwitchBot initialized for channel: {self._channel}")
+
+    async def event_ready(self):
+        """Called when the bot successfully connects to Twitch."""
+        logger.info(f"Twitch Bot logged in as: {self.nick}")
+        logger.info(f"Connected to channels: {[c.name for c in self.connected_channels]}")
+
+    async def event_message(self, message):
+        """Called when a message is received in chat."""
+        # Ignore messages from the bot itself
+        if message.echo:
+            return
+
+        # Handle commands first
+        await self.handle_commands(message)
+
+        # Extract user and message content
+        author = message.author
+        if author is None:
+            return
+
+        username = author.name
+        content = message.content.strip()
+
+        # Log the message for debugging
+        logger.info(f"Twitch chat [{username}]: {content}")
+
+        # Forward to game engine for command processing
+        try:
+            await self._game_engine.process_command(username, content)
+        except Exception as e:
+            logger.error(f"Error processing command: {e}")
+
+        # Check for bits in the message tags
+        if hasattr(message, 'tags') and message.tags:
+            bits = message.tags.get('bits')
+            if bits:
+                try:
+                    bits_amount = int(bits)
+                    logger.info(f"Received {bits_amount} bits from {username}")
+                    await self._game_engine.process_bits(username, bits_amount)
+
+                    # Send special gift effect to Unity
+                    await self._game_engine._broadcast_event("gift_effect", {
+                        "type": "gift_effect",
+                        "user": username,
+                        "value": bits_amount,
+                        "message": f"{username} cheered {bits_amount} bits!"
+                    })
+                except (ValueError, TypeError) as e:
+                    logger.error(f"Error parsing bits amount: {e}")
+
+    async def event_command_error(self, context, error):
+        """Called when a command error occurs."""
+        # Ignore command not found errors (most chat messages aren't commands)
+        if isinstance(error, commands.CommandNotFound):
+            return
+        logger.error(f"Command error: {error}")
+
+    async def event_error(self, error: Exception, data: str = None):
+        """Called when an error occurs."""
+        logger.error(f"Twitch bot error: {error}")
+        if data:
+            logger.debug(f"Error data: {data}")