feat: add all application source code

- apps/api: FastAPI backend with Dockerfile
- apps/web: Next.js frontend with Dockerfile
- apps/sensor: Signal collection agent
- packages: shared packages

Co-Authored-By: Claude <noreply@anthropic.com>

apps/api/src/services/notifications/__init__.py

@@ -0,0 +1,24 @@
+"""
+leWOOOgo Notification System
+=============================
+Phase 6: Output Plugins 生態系
+
+NotificationProvider 介面 + 具體實作:
+- DiscordWebhookProvider
+- SlackWebhookProvider (TODO)
+- LineNotifyProvider (TODO)
+"""
+
+from .base import NotificationProvider, NotificationMessage, NotificationResult, ExecutionStatus
+from .discord import DiscordWebhookProvider
+from .manager import NotificationManager, get_notification_manager
+
+__all__ = [
+    "NotificationProvider",
+    "NotificationMessage",
+    "NotificationResult",
+    "ExecutionStatus",
+    "DiscordWebhookProvider",
+    "NotificationManager",
+    "get_notification_manager",
+]