Add the shared Claude Remote Control setup

Units, settings and setup README for the claude-rc user, which serves my projects' read-only MCP servers to the Claude app (negsplit for now).

.config/claude-rc/claude-rc-notify.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Notify via ntfy that Claude Remote Control stopped
+
+[Service]
+Type=oneshot
+DynamicUser=yes
+# NTFY_TOPIC=...: root-only (0600), the topic is the only secret
+EnvironmentFile=/etc/claude-rc-notify.env
+TimeoutStartSec=10min
+ExecStart=/usr/bin/curl -fsS -m 30 --retry 5 --retry-delay 60 --retry-all-errors \
+    -H "Title: Claude Remote Control stopped" -H "Tags: warning" \
+    -d "%H: claude-rc.service keeps failing (dead login?). Retried every 3 h; fix at home: claude auth login as claude-rc." \
+    https://ntfy.sh/${NTFY_TOPIC}