refactor(api): resolve sudo/systemctl/reboot/poweroff paths at startup

Use shutil.which() with safe fallbacks for the four privileged binaries
instead of relying on bare names being resolved by the subprocess shell
search. Resolves paths once at module load rather than per-call.

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

web_interface/blueprints/api_v3.py

@@ -2,6 +2,7 @@ from flask import Blueprint, request, jsonify, Response, send_from_directory
 import json
 import os
 import re
+import shutil
 import socket
 import sys
 import subprocess
@@ -16,6 +17,11 @@ from typing import Optional, Tuple, Dict, Any, Type
 
 logger = logging.getLogger(__name__)
 
+SUDO_BIN = shutil.which("sudo") or "/usr/bin/sudo"
+SYSTEMCTL_BIN = shutil.which("systemctl") or "/usr/bin/systemctl"
+REBOOT_BIN = shutil.which("reboot") or "/usr/sbin/reboot"
+POWEROFF_BIN = shutil.which("poweroff") or "/usr/sbin/poweroff"
+
 # Import new infrastructure
 from src.web_interface.api_helpers import success_response, error_response, validate_request_json
 from src.web_interface.errors import ErrorCode
@@ -218,7 +224,7 @@ def _ensure_display_service_running():
     if status.get('active'):
         status['started'] = False
         return status
-    result = _run_systemctl_command(['sudo', 'systemctl', 'start', 'ledmatrix.service'])
+    result = _run_systemctl_command([SUDO_BIN, SYSTEMCTL_BIN, 'start', 'ledmatrix.service'])
     service_status = _get_display_service_status()
     result['started'] = result.get('returncode') == 0
     result['active'] = service_status.get('active')
@@ -227,7 +233,7 @@ def _ensure_display_service_running():
 
 def _stop_display_service():
     """Stop the ledmatrix display service."""
-    result = _run_systemctl_command(['sudo', 'systemctl', 'stop', 'ledmatrix.service'])
+    result = _run_systemctl_command([SUDO_BIN, SYSTEMCTL_BIN, 'stop', 'ledmatrix.service'])
     status = _get_display_service_status()
     result['active'] = status.get('active')
     result['status'] = status
@@ -1716,7 +1722,7 @@ def execute_system_action():
             if mode:
                 # For on-demand modes, we would need to integrate with the display controller
                 # For now, just start the display service
-                result = subprocess.run(['sudo', 'systemctl', 'start', 'ledmatrix.service'],
+                result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'start', 'ledmatrix.service'],
                                      capture_output=True, text=True, timeout=15)
                 return jsonify({
                     'status': 'success' if result.returncode == 0 else 'error',
@@ -1727,22 +1733,22 @@ def execute_system_action():
                     'stderr': result.stderr
                 })
             else:
-                result = subprocess.run(['sudo', 'systemctl', 'start', 'ledmatrix.service'],
+                result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'start', 'ledmatrix.service'],
                                      capture_output=True, text=True, timeout=15)
         elif action == 'stop_display':
-            result = subprocess.run(['sudo', 'systemctl', 'stop', 'ledmatrix.service'],
+            result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'stop', 'ledmatrix.service'],
                                  capture_output=True, text=True, timeout=15)
         elif action == 'enable_autostart':
-            result = subprocess.run(['sudo', 'systemctl', 'enable', 'ledmatrix.service'],
+            result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'enable', 'ledmatrix.service'],
                                  capture_output=True, text=True, timeout=15)
         elif action == 'disable_autostart':
-            result = subprocess.run(['sudo', 'systemctl', 'disable', 'ledmatrix.service'],
+            result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'disable', 'ledmatrix.service'],
                                  capture_output=True, text=True, timeout=15)
         elif action == 'reboot_system':
-            result = subprocess.run(['sudo', 'reboot'],
+            result = subprocess.run([SUDO_BIN, REBOOT_BIN],
                                  capture_output=True, text=True, timeout=10)
         elif action == 'shutdown_system':
-            result = subprocess.run(['sudo', 'poweroff'],
+            result = subprocess.run([SUDO_BIN, POWEROFF_BIN],
                                  capture_output=True, text=True, timeout=10)
         elif action == 'git_pull':
             # Use PROJECT_ROOT instead of hardcoded path
@@ -1824,10 +1830,10 @@ def execute_system_action():
                 'stderr': result.stderr
             })
         elif action == 'restart_display_service':
-            result = subprocess.run(['sudo', 'systemctl', 'restart', 'ledmatrix.service'],
+            result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'restart', 'ledmatrix.service'],
                                  capture_output=True, text=True, timeout=15)
         elif action == 'restart_web_service':
-            result = subprocess.run(['sudo', 'systemctl', 'restart', 'ledmatrix-web.service'],
+            result = subprocess.run([SUDO_BIN, SYSTEMCTL_BIN, 'restart', 'ledmatrix-web.service'],
                                  capture_output=True, text=True, timeout=15)
         else:
             return jsonify({'status': 'error', 'message': f'Unknown action: {action}'}), 400