feat: keenetic integration, VPN alerts, docs

Wire keenetic monitor loop and router into main app. Add deduplicated
Telegram alerts for router offline, internet, CPU/RAM, and VPN down.
Update README with KeenDNS edit, import format, troubleshooting.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/services/notifier.py

@@ -30,7 +30,13 @@ async def send_telegram(message: str, parse_mode: str = "Markdown"):
                 "text": message,
                 "parse_mode": parse_mode,
             }) as resp:
-                return resp.status == 200
+                ok = resp.status == 200
+                if ok:
+                    logger.info(f"Telegram sent: {message[:80]}")
+                else:
+                    body = await resp.text()
+                    logger.error(f"Telegram send HTTP {resp.status}: {body[:200]}")
+                return ok
     except Exception as e:
         logger.error(f"Telegram send error: {e}")
         return False