Initial commit: cert-manager API server

FastAPI-based SSL certificate automation server.
- Google Public CA wildcard cert issuance via certbot
- Cloudflare DNS-01 challenge with auto EAB key generation
- APISIX multi-instance deployment with domain-instance mapping
- Vault integration for all secrets
- Bearer token auth, retry logic, Discord DM alerts
- Auto-renewal scheduler (daily 03:00 UTC)

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

app/alert.py

@@ -0,0 +1,43 @@
+import logging
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+DISCORD_API = "https://discord.com/api/v10"
+
+
+async def send_discord_dm(bot_token: str, user_id: str, message: str) -> bool:
+    """Discord DM으로 알림 전송."""
+    if not bot_token or not user_id:
+        logger.warning("Discord credentials not configured, skipping alert")
+        return False
+
+    headers = {
+        "Authorization": f"Bot {bot_token}",
+        "Content-Type": "application/json",
+    }
+
+    try:
+        async with httpx.AsyncClient(timeout=15) as client:
+            # DM 채널 생성
+            resp = await client.post(
+                f"{DISCORD_API}/users/@me/channels",
+                headers=headers,
+                json={"recipient_id": user_id},
+            )
+            resp.raise_for_status()
+            channel_id = resp.json()["id"]
+
+            # 메시지 전송
+            resp = await client.post(
+                f"{DISCORD_API}/channels/{channel_id}/messages",
+                headers=headers,
+                json={"content": message},
+            )
+            resp.raise_for_status()
+            logger.info("Discord alert sent to user %s", user_id)
+            return True
+    except Exception as e:
+        logger.error("Failed to send Discord alert: %s", e)
+        return False