feat: improve legacy agent detection and migration UX

Add seamless migration path from legacy agents to unified agent:

- Add AgentType field to report payloads (unified vs legacy detection)
- Update server to detect legacy agents by type instead of version
- Add UI banner showing upgrade command when legacy agents are detected
- Add deprecation notice to install-host-agent.ps1
- Create install-docker-agent.sh stub that redirects to unified installer

Legacy agents (pulse-host-agent, pulse-docker-agent) now show a "Legacy"
badge in the UI with a one-click copy command to upgrade to the unified
agent.

scripts/install-docker-agent.sh

@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+#
+# DEPRECATED: pulse-docker-agent installer
+#
+# This script is deprecated. Please use the unified agent instead:
+#
+#   curl -fsSL http://<pulse-server>:7655/install.sh | \
+#     sudo bash -s -- --url http://<pulse-server>:7655 --token <token> --enable-docker
+#
+# The unified agent provides:
+#   - Combined host + Docker monitoring in one binary
+#   - Automatic updates
+#   - Simplified management
+#
+# This script will redirect you to the unified agent installer.
+#
+
+set -euo pipefail
+
+echo ""
+echo "┌─────────────────────────────────────────────────────────────────────────────┐"
+echo "│  DEPRECATED: pulse-docker-agent has been replaced by the unified agent.     │"
+echo "│                                                                             │"
+echo "│  The unified agent provides:                                                │"
+echo "│    • Combined host + Docker monitoring in one binary                        │"
+echo "│    • Automatic updates                                                      │"
+echo "│    • Simplified management                                                  │"
+echo "│                                                                             │"
+echo "│  Installing unified agent instead...                                        │"
+echo "└─────────────────────────────────────────────────────────────────────────────┘"
+echo ""
+
+# Parse arguments to extract URL and token for redirection
+PULSE_URL=""
+PULSE_TOKEN=""
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --url) PULSE_URL="$2"; shift 2 ;;
+        --token) PULSE_TOKEN="$2"; shift 2 ;;
+        *) shift ;; # ignore other args
+    esac
+done
+
+if [[ -z "$PULSE_URL" ]]; then
+    echo "[ERROR] --url is required"
+    echo ""
+    echo "Usage:"
+    echo "  curl -fsSL http://<pulse-server>:7655/install.sh | \\"
+    echo "    sudo bash -s -- --url http://<pulse-server>:7655 --token <token> --enable-docker"
+    exit 1
+fi
+
+if [[ -z "$PULSE_TOKEN" ]]; then
+    echo "[ERROR] --token is required"
+    echo ""
+    echo "Usage:"
+    echo "  curl -fsSL ${PULSE_URL}/install.sh | \\"
+    echo "    sudo bash -s -- --url ${PULSE_URL} --token <token> --enable-docker"
+    exit 1
+fi
+
+# Download and run the unified installer with --enable-docker
+echo "[INFO] Downloading unified agent installer..."
+curl -fsSL "${PULSE_URL}/install.sh" | bash -s -- --url "$PULSE_URL" --token "$PULSE_TOKEN" --enable-docker

scripts/install-host-agent.ps1

@@ -1,5 +1,19 @@
 # Pulse Host Agent Installation Script for Windows
 #
+# ┌─────────────────────────────────────────────────────────────────────────────┐
+# │  DEPRECATED: This script installs the legacy pulse-host-agent.              │
+# │  Please use the unified agent instead:                                      │
+# │                                                                             │
+# │    $env:PULSE_URL="http://pulse-server:7655"                                │
+# │    $env:PULSE_TOKEN="your-token"                                            │
+# │    irm http://pulse-server:7655/install.ps1 | iex                           │
+# │                                                                             │
+# │  The unified agent provides:                                                │
+# │    - Combined host + Docker monitoring in one binary                        │
+# │    - Automatic updates                                                      │
+# │    - Simplified management                                                  │
+# └─────────────────────────────────────────────────────────────────────────────┘
+#
 # Usage:
 #   iwr -useb http://pulse-server:7656/install-host-agent.ps1 | iex
 #   OR with parameters: