feat: frps-manager v1.0 - frp 0.70.1 multi-tenant web management system

- Multi-tenant client/proxy management with Flask+SQLite
- Frps server control (start/restart/token rotation)
- Generate frpc.ini with shared server token + admin API
- Dashboard API integration (live client/proxy status)
- RBAC: admin/tenant_admin/user roles
- Audit logging for all operations
- Systemd service files included
- Requires legacy INI format (frp 0.70 TOML auth broken)

runtime/frpc@.service

@@ -0,0 +1,22 @@
+# Example frpc systemd unit. Copy to /etc/systemd/system/frpc@.service on
+# the frpc host, then:
+#   systemctl daemon-reload
+#   systemctl enable --now frpc@<client-name>.service
+#
+# The <instance> specifier lets you run multiple frpc instances per host.
+# Place per-instance configs under /etc/frpc/<instance>.ini.
+
+[Unit]
+Description=frpc — fatedier/frp client (%i)
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/local/bin/frpc -c /etc/frpc/%i.ini
+Restart=on-failure
+RestartSec=5
+LimitNOFILE=65536
+
+[Install]
+WantedBy=multi-user.target