refactor: deploy model — all files under /opt/pulse-lets-go

Single prefix deployment: /opt/pulse-lets-go/ contains
bin/, data/, web/, log/ — no more split across
/usr/local/bin, /etc, /usr/local/share, /var/log.

* Makefile: install → deploy target with PREFIX=/opt/pulse-lets-go
* deploy/pulse-lets-go.service: all paths under /opt/pulse-lets-go,
  removed stale nats.service dependency
* main.go: default dataDir = parent of exeDir (PREFIX/bin → PREFIX/data)
* README: updated all paths, step 1 uses make deploy

deploy/pulse-lets-go.service

@@ -1,16 +1,14 @@
 [Unit]
 Description=pulse-lets-go — Telephone Load Balancer
 Documentation=https://github.com/pulse-lets-go
-After=network.target nats.service
-Wants=nats.service
+After=network.target
 
 [Service]
 Type=simple
 User=pulse
 Group=pulse
-ExecStart=/usr/local/bin/pulse-lets-go
-WorkingDirectory=/usr/local/share/pulse-lets-go
-Environment=PULSE_DATA_DIR=/etc/pulse-lets-go
+ExecStart=/opt/pulse-lets-go/bin/pulse-lets-go
+WorkingDirectory=/opt/pulse-lets-go
 Restart=always
 RestartSec=5
 
@@ -19,7 +17,7 @@ NoNewPrivileges=yes
 PrivateTmp=yes
 ProtectSystem=strict
 ProtectHome=yes
-ReadWritePaths=/etc/pulse-lets-go /var/log/pulse-lets-go
+ReadWritePaths=/opt/pulse-lets-go/data /opt/pulse-lets-go/log
 
 # Логирование
 StandardOutput=journal