feat: add heartbeat-poc.py for end-to-end pipeline testing

- heartbeat-poc.py: Python script gửi heartbeat lên API
  - Chạy trên Pi 4
  - Gửi CPU temp, battery, disk, network status
  - 30s interval (configurable)
- seed.ts: fix device ID = serial (DEMO-001/002/003)
  - API key: dev-api-key-demo-001|002|003
  - Credential output in console

POC flow: Pi → heartbeat-poc.py → /v1/devices/DEMO-001/heartbeat
          → API → WebSocket → Dashboard live update

apps/api-server/src/db/seed.ts

@@ -64,7 +64,7 @@ async function seed() {
   ]
 
   for (const d of deviceNames) {
-    const deviceId = nanoid()
+    const deviceId = d.serial  // ID = serial for easy POC testing
     const apiKeyHash = `dev-api-key-${d.serial.toLowerCase()}`
     await db.insert(devices).values({
       id: deviceId,
@@ -77,7 +77,7 @@ async function seed() {
       firmwareVersion: '1.0.0',
       lastSeenAt: new Date(),
     })
-    console.log(`  ✓ Device: ${d.name} (${d.serial}) — API key: ${apiKeyHash}`)
+    console.log(`  ✓ Device: ${d.name} (${d.serial}) — API key: ${apiKeyHash} — ID: ${deviceId}`)
   }
 
   console.log('\n✅ Seed complete!')

apps/device-agent/heartbeat-poc.py

@@ -0,0 +1,141 @@
+#!/usr/bin/env python3
+"""
+heartbeat-poc.py — Proof of Concept heartbeat sender
+
+Run on Pi 4 to test end-to-end pipeline:
+  Pi → API → WebSocket → Dashboard
+
+Usage:
+  python3 heartbeat-poc.py
+
+Requirements:
+  pip install requests
+"""
+
+import os
+import sys
+import time
+import json
+import subprocess
+import argparse
+from datetime import datetime
+
+# ── Config ──────────────────────────────────────────────────────
+API_BASE = os.environ.get('API_BASE', 'http://localhost:3001')
+DEVICE_ID = os.environ.get('DEVICE_ID', 'DEMO-001')   # khớp với seed
+API_KEY = os.environ.get('API_KEY', 'dev-api-key-demo-001')  # khớp với seed
+INTERVAL_SECONDS = int(os.environ.get('INTERVAL_SECONDS', 30))
+
+
+def get_device_info() -> dict:
+    """Gather device telemetry — stub cho POC."""
+    try:
+        # Nhiệt độ CPU (Linux)
+        with open('/sys/class/thermal/thermal_zone0/temp') as f:
+            temp_milli = int(f.read().strip())
+            temp_c = round(temp_milli / 1000, 1)
+    except Exception:
+        temp_c = None
+
+    try:
+        # Battery (nếu có)
+        result = subprocess.run(
+            ['cat', '/sys/class/power_supply/BAT0/capacity'],
+            capture_output=True, text=True
+        )
+        battery = int(result.stdout.strip()) if result.returncode == 0 else None
+    except Exception:
+        battery = None
+
+    try:
+        # Disk free (GB)
+        result = subprocess.run(
+            ['df', '-BG', '--output=avail', '/'],
+            capture_output=True, text=True
+        )
+        lines = result.stdout.strip().split('\n')
+        if len(lines) >= 2:
+            free_str = lines[1].strip().rstrip('G')
+            storage_free = int(free_str)
+        else:
+            storage_free = 50
+    except Exception:
+        storage_free = 50
+
+    try:
+        # Network status
+        result = subprocess.run(
+            ['ping', '-c1', '-W1', '8.8.8.8'],
+            capture_output=True
+        )
+        network_status = 'online' if result.returncode == 0 else 'degraded'
+    except Exception:
+        network_status = 'online'
+
+    return {
+        'tempC': temp_c,
+        'batteryPct': battery,
+        'storageFreeGb': storage_free,
+        'networkStatus': network_status,
+        'lastCaptureAt': datetime.utcnow().isoformat(),
+        'capturesToday': 0,
+    }
+
+
+def send_heartbeat(device_id: str, api_key: str) -> bool:
+    """Gửi heartbeat lên API."""
+    import requests
+
+    payload = {
+        'deviceId': device_id,
+        'apiKey': api_key,
+        'status': 'online',
+        'firmwareVersion': 'poc-1.0.0',
+        **get_device_info(),
+    }
+
+    url = f'{API_BASE}/v1/devices/{device_id}/heartbeat'
+
+    try:
+        resp = requests.post(url, json=payload, timeout=10)
+        if resp.ok:
+            data = resp.json()
+            print(f"[{datetime.now().strftime('%H:%M:%S')}] "
+                  f"✓ heartbeat sent | pending commands: {data.get('pendingCommands', 0)}")
+            return True
+        else:
+            print(f"[{datetime.now().strftime('%H:%M:%S')}] "
+                  f"✗ API error {resp.status_code}: {resp.text[:100]}")
+            return False
+    except Exception as e:
+        print(f"[{datetime.now().strftime('%H:%M:%S')}] ✗ connection error: {e}")
+        return False
+
+
+def main():
+    parser = argparse.ArgumentParser(description='POC Heartbeat Sender')
+    parser.add_argument('--device-id', default=DEVICE_ID, help='Device ID')
+    parser.add_argument('--api-key', default=API_KEY, help='API Key')
+    parser.add_argument('--interval', type=int, default=INTERVAL_SECONDS, help='Seconds between heartbeats')
+    parser.add_argument('--once', action='store_true', help='Send once and exit')
+    args = parser.parse_args()
+
+    print(f'=== Heartbeat POC ===')
+    print(f'  Device:    {args.device_id}')
+    print(f'  API:       {API_BASE}')
+    print(f'  Interval:  {args.interval}s')
+    print(f'  Dashboard: http://localhost:3000')
+    print()
+
+    if args.once:
+        send_heartbeat(args.device_id, args.api_key)
+        return
+
+    print('Press Ctrl+C to stop.\n')
+    while True:
+        send_heartbeat(args.device_id, args.api_key)
+        time.sleep(args.interval)
+
+
+if __name__ == '__main__':
+    main()