feat: push-based monitoring with remote agent

- Add database migration 006 for agent_key, agent_installed, agent_install_path, agent_last_seen_at columns
- Add Server model methods: findByAgentKey, generateAgentKey, regenerateAgentKey, updateAgentLastSeen, setAgentInstalled
- Auto-generate agent_key on server creation
- Create AgentService for SSH-based install/uninstall of remote agent
- Create bin/agent.sh - bash agent script for remote servers
- Create install/agent-install.sh and install/agent-uninstall.sh
- Create install/servermanager-agent.service systemd unit
- Add POST /api/metrics/push endpoint (auth via agent_key)
- Add web routes for agent install/uninstall/regenerate-key
- Add agent status section to server detail view with install/uninstall modals
- Make MonitoringService::saveMetrics() public for reuse

install/agent-install.sh

@@ -0,0 +1,136 @@
+#!/bin/bash
+# ServerManager Agent Installer
+# Usage: bash agent-install.sh <SERVER_URL> <AGENT_KEY> [INTERVAL]
+set -e
+
+SERVER_URL="${1:-}"
+AGENT_KEY="${2:-}"
+INTERVAL="${3:-60}"
+
+if [ -z "$SERVER_URL" ] || [ -z "$AGENT_KEY" ]; then
+    echo "Usage: bash agent-install.sh <SERVER_URL> <AGENT_KEY> [INTERVAL]"
+    exit 1
+fi
+
+AGENT_BIN="/usr/local/bin/servermanager-agent"
+CONFIG_DIR="/etc/servermanager"
+CONFIG_FILE="$CONFIG_DIR/agent.conf"
+SERVICE_FILE="/etc/systemd/system/servermanager-agent.service"
+
+echo "[1/5] Creating config directory..."
+mkdir -p "$CONFIG_DIR"
+
+echo "[2/5] Installing agent binary..."
+cat > "$AGENT_BIN" << 'AGENTSCRIPT'
+#!/bin/bash
+set -e
+CONFIG_FILE="/etc/servermanager/agent.conf"
+
+load_config() {
+    if [ -f "$CONFIG_FILE" ]; then
+        source "$CONFIG_FILE"
+    fi
+    SERVER_URL="${SERVER_URL:-}"
+    AGENT_KEY="${AGENT_KEY:-}"
+    INTERVAL="${INTERVAL:-60}"
+}
+
+collect_metrics() {
+    CPU=$(top -bn1 2>/dev/null | grep 'Cpu(s)' | awk '{print $2}' | cut -d'%' -f1)
+    [ -z "$CPU" ] && CPU=0
+    RAM=$(free 2>/dev/null | grep Mem | awk '{printf "%.1f", $3/$2 * 100}')
+    [ -z "$RAM" ] && RAM=0
+    DISK=$(df / 2>/dev/null | tail -1 | awk '{print $5}' | sed 's/%//')
+    [ -z "$DISK" ] && DISK=0
+    LOAD=$(cat /proc/loadavg 2>/dev/null | awk '{print $1}')
+    [ -z "$LOAD" ] && LOAD=0
+    UPTIME=$(uptime -p 2>/dev/null | sed 's/^up //')
+    [ -z "$UPTIME" ] && UPTIME=""
+}
+
+push_metrics() {
+    local payload
+    payload=$(cat <<EOF
+{
+    "agent_key": "$AGENT_KEY",
+    "cpu": $CPU,
+    "ram": $RAM,
+    "disk": $DISK,
+    "load": $LOAD,
+    "uptime": "$UPTIME"
+}
+EOF
+)
+    curl -s -X POST "$SERVER_URL/api/metrics/push" \
+        -H "Content-Type: application/json" \
+        -d "$payload" \
+        --connect-timeout 10 --max-time 30 \
+        -o /dev/null -w "%{http_code}" 2>/dev/null || echo "000"
+}
+
+main() {
+    load_config
+    if [ -z "$SERVER_URL" ] || [ -z "$AGENT_KEY" ]; then
+        echo "ERROR: SERVER_URL and AGENT_KEY must be set in $CONFIG_FILE"
+        exit 1
+    fi
+    echo "ServerManager Agent started (interval: ${INTERVAL}s)"
+    sleep 5
+    while true; do
+        collect_metrics
+        http_code=$(push_metrics)
+        if [ "$http_code" = "200" ]; then
+            echo "[$(date)] Metrics pushed successfully"
+        else
+            echo "[$(date)] Failed to push metrics (HTTP $http_code)"
+        fi
+        sleep "$INTERVAL"
+    done
+}
+main
+AGENTSCRIPT
+chmod +x "$AGENT_BIN"
+
+echo "[3/5] Writing config..."
+cat > "$CONFIG_FILE" << EOF
+SERVER_URL="$SERVER_URL"
+AGENT_KEY="$AGENT_KEY"
+INTERVAL=$INTERVAL
+EOF
+chmod 600 "$CONFIG_FILE"
+
+echo "[4/5] Installing systemd service..."
+cat > "$SERVICE_FILE" << 'UNIT'
+[Unit]
+Description=ServerManager Monitoring Agent
+Documentation=https://github.com/servermanager
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/local/bin/servermanager-agent
+Restart=always
+RestartSec=10
+StartLimitIntervalSec=60
+StartLimitBurst=5
+NoNewPrivileges=yes
+ProtectSystem=full
+ProtectHome=yes
+PrivateDevices=yes
+PrivateTmp=yes
+
+[Install]
+WantedBy=multi-user.target
+UNIT
+
+echo "[5/5] Enabling and starting service..."
+systemctl daemon-reload
+systemctl enable servermanager-agent
+systemctl restart servermanager-agent
+
+echo ""
+echo "ServerManager Agent installed successfully!"
+echo "  Binary: $AGENT_BIN"
+echo "  Config: $CONFIG_FILE"
+echo "  Service: $SERVICE_FILE"

install/agent-uninstall.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# ServerManager Agent Uninstaller
+set -e
+
+AGENT_BIN="/usr/local/bin/servermanager-agent"
+CONFIG_DIR="/etc/servermanager"
+SERVICE_FILE="/etc/systemd/system/servermanager-agent.service"
+
+echo "[1/3] Stopping and disabling service..."
+systemctl stop servermanager-agent 2>/dev/null || true
+systemctl disable servermanager-agent 2>/dev/null || true
+systemctl daemon-reload
+
+echo "[2/3] Removing files..."
+rm -f "$AGENT_BIN"
+rm -rf "$CONFIG_DIR"
+rm -f "$SERVICE_FILE"
+
+echo "[3/3] Reloading systemd..."
+systemctl daemon-reload
+
+echo "ServerManager Agent uninstalled successfully."

install/servermanager-agent.service

@@ -0,0 +1,21 @@
+[Unit]
+Description=ServerManager Monitoring Agent
+Documentation=https://github.com/servermanager
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+ExecStart=/usr/local/bin/servermanager-agent
+Restart=always
+RestartSec=10
+StartLimitIntervalSec=60
+StartLimitBurst=5
+NoNewPrivileges=yes
+ProtectSystem=full
+ProtectHome=yes
+PrivateDevices=yes
+PrivateTmp=yes
+
+[Install]
+WantedBy=multi-user.target