feat(service): implement PID-file based service management (DAW/furt#100)

- Replace unreliable pexp patterns with PID-file approach
- Add graceful shutdown with timeout handling in rc.d script
- Implement process validation after startup
- Add SIGHUP config reload support for Unix services
- Ensure PID-file cleanup on service exit
- Update systemd service to use PIDFile parameter

Platform improvements:
- OpenBSD: rc_check/rc_stop functions now PID-file based
- Linux: systemd Type=forking with proper PIDFile support
- Cross-platform: /var/run/furt.pid standard location

Resolves service status detection issues where rcctl check showed
(failed) despite running service due to process name variations
across platforms.

deployment/openbsd/rc.d-furt

@@ -3,11 +3,52 @@
 daemon="/usr/local/share/furt/scripts/start.sh"
 daemon_user="_furt"
 daemon_cwd="/usr/local/share/furt"
-daemon_flags="start"
 
 . /etc/rc.d/rc.subr
 
-pexp="lua.*src/main.lua"
+# PID-File location
+pidfile="/var/run/furt.pid"
+
+# Custom rc_check function (PID-File based)
+rc_check() {
+    [ -f "$pidfile" ] && kill -0 $(cat "$pidfile") 2>/dev/null
+}
+
+# Custom rc_stop function (PID-File based)
+rc_stop() {
+    if [ -f "$pidfile" ]; then
+        local _pid=$(cat "$pidfile")
+        echo "Stopping furt (PID: $_pid)"
+        kill "$_pid" 2>/dev/null
+        # Wait for process to die
+        local _timeout=10
+        while [ $_timeout -gt 0 ] && kill -0 "$_pid" 2>/dev/null; do
+            sleep 1
+            _timeout=$((_timeout - 1))
+        done
+        # Force kill if still running
+        if kill -0 "$_pid" 2>/dev/null; then
+            echo "Force killing furt (PID: $_pid)"
+            kill -9 "$_pid" 2>/dev/null
+        fi
+        rm -f "$pidfile"
+        echo "furt stopped"
+    else
+        echo "furt not running (no PID-File)"
+    fi
+}
+
+# Custom rc_reload function (signal-based)
+rc_reload() {
+    if rc_check; then
+        local _pid=$(cat "$pidfile")
+        echo "Reloading furt configuration (PID: $_pid)"
+        kill -HUP "$_pid"
+    else
+        echo "furt not running"
+        return 1
+    fi
+}
 
 rc_cmd $1