Add system memory monitoring, Bedrock support, and Discord integrations

- Add CPU/GPU memory monitoring endpoint and frontend widget
- Add Amazon Bedrock model support (API key / inference profiles) plus model selector entries
- Add Discord weather/laundry notification job (JMA forecast + LLM-generated message)
- Add Discord bot that replies to mentions via the configured LLM, with weather-aware context
- Add scheduled "useless tips" job with separate webhook and quiet-hours skip
- Switch FastAPI startup to lifespan handler, log viewer, markdown rendering, and toast UI additions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/core/notify.py

@@ -0,0 +1,13 @@
+"""Discord Webhook への通知送信。"""
+import logging
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+
+async def send_discord_message(webhook_url: str, content: str) -> None:
+    async with httpx.AsyncClient(timeout=10.0) as client:
+        response = await client.post(webhook_url, json={"content": content})
+        response.raise_for_status()
+        logger.info("Discord message sent (status=%s)", response.status_code)