Add HTTP health check endpoint on port 9102

Lightweight /health endpoint returns JSON with status, hostname, and
last check timestamp. Runs as daemon thread, activated via --health-server
flag or HEALTH_SERVER_ENABLED=true in .env config.

Fixes: #21

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hwmonDaemon.py

@@ -130,7 +130,10 @@ class SystemHealthMonitor:
         'NEW_DRIVE_HOURS_THRESHOLD': 720,    # Hours to consider a drive "new" (~30 days)
         'SMART_ERROR_RECENT_HOURS': 168,     # Hours window for recent SMART errors (~1 week)
         # Storage limits
-        'HISTORY_MAX_BYTES': 52428800         # 50MB max storage for history files
+        'HISTORY_MAX_BYTES': 52428800,        # 50MB max storage for history files
+        # Health check endpoint
+        'HEALTH_SERVER_ENABLED': False,  # Enable HTTP health check endpoint
+        'HEALTH_SERVER_PORT': 9102       # Port for health check endpoint
     }
 
     @classmethod
@@ -212,6 +215,15 @@ class SystemHealthMonitor:
                                 cls.CONFIG['HISTORY_MAX_BYTES'] = int(value)
                             except ValueError:
                                 logger.warning(f"Invalid HISTORY_MAX_BYTES value: {value}")
+                        # Health server settings
+                        elif key == 'HEALTH_SERVER_ENABLED':
+                            cls.CONFIG['HEALTH_SERVER_ENABLED'] = value.lower() in ('true', '1', 'yes')
+                            logger.info(f"✓ Loaded HEALTH_SERVER_ENABLED: {cls.CONFIG['HEALTH_SERVER_ENABLED']}")
+                        elif key == 'HEALTH_SERVER_PORT':
+                            try:
+                                cls.CONFIG['HEALTH_SERVER_PORT'] = int(value)
+                            except ValueError:
+                                logger.warning(f"Invalid HEALTH_SERVER_PORT value: {value}")
 
         except Exception as e:
             logger.error(f"Failed to load .env file: {e}")
@@ -669,6 +681,10 @@ class SystemHealthMonitor:
         # Drive details cache (per-run, cleared on next execution)
         self._drive_details_cache = {}
 
+        # Health check tracking
+        self._last_check_timestamp = None
+        self._last_check_status = 'unknown'
+
         # Check tool availability at startup
         self._available_tools = self._check_tool_availability()
 
@@ -751,6 +767,45 @@ class SystemHealthMonitor:
         except Exception as e:
             logger.error(f"Error enforcing storage limit: {e}")
 
+    # =============================================================================
+    # HEALTH CHECK ENDPOINT
+    # =============================================================================
+    def _start_health_server(self):
+        """Start a lightweight HTTP health check endpoint as a daemon thread."""
+        from http.server import HTTPServer, BaseHTTPRequestHandler
+        import threading
+
+        monitor = self
+
+        class HealthHandler(BaseHTTPRequestHandler):
+            def do_GET(self):
+                if self.path == '/health':
+                    response = {
+                        'status': monitor._last_check_status,
+                        'hostname': socket.gethostname(),
+                        'last_check': monitor._last_check_timestamp,
+                        'uptime': datetime.datetime.now().isoformat()
+                    }
+                    self.send_response(200)
+                    self.send_header('Content-Type', 'application/json')
+                    self.end_headers()
+                    self.wfile.write(json.dumps(response).encode())
+                else:
+                    self.send_response(404)
+                    self.end_headers()
+
+            def log_message(self, format, *args):
+                logger.debug(f"Health server: {format % args}")
+
+        port = self.CONFIG.get('HEALTH_SERVER_PORT', 9102)
+        try:
+            server = HTTPServer(('', port), HealthHandler)
+            thread = threading.Thread(target=server.serve_forever, daemon=True)
+            thread.start()
+            logger.info(f"Health check endpoint started on port {port}")
+        except OSError as e:
+            logger.warning(f"Could not start health server on port {port}: {e}")
+
     # =============================================================================
     # MAIN EXECUTION METHODS
     # =============================================================================
@@ -760,6 +815,10 @@ class SystemHealthMonitor:
             # Perform health checks and gather the report
             health_report = self.perform_health_checks()
 
+            # Track last check for health endpoint
+            self._last_check_timestamp = datetime.datetime.now().isoformat()
+            self._last_check_status = health_report.get('drives_health', {}).get('overall_status', 'unknown')
+
             # Create tickets for any detected critical issues
             self._create_tickets_for_issues(health_report)
 
@@ -3625,6 +3684,11 @@ def main():
         action="store_true",
         help="Enable verbose (DEBUG) logging output."
     )
+    parser.add_argument(
+        "--health-server",
+        action="store_true",
+        help="Start HTTP health check endpoint (default port 9102)."
+    )
     args = parser.parse_args()
 
     monitor = SystemHealthMonitor(
@@ -3633,6 +3697,10 @@ def main():
         verbose=args.verbose
     )
 
+    # Start health server if requested via CLI or .env
+    if args.health_server or monitor.CONFIG.get('HEALTH_SERVER_ENABLED', False):
+        monitor._start_health_server()
+
     if args.metrics:
         # Just output metrics to stdout
         health_report = monitor.perform_health_checks()