Fix dashcam mount-point creation permission error

mount_device() used a bare os.makedirs() to create the mount point,
but the app runs as an unprivileged user while /mnt is root-owned -
surfaced as a real PermissionError during the first actual hardware
test. Create the mount point via sudo mkdir -p instead, consistent
with the existing sudo mount/umount calls in this module.

Co-authored-by: Copilot <[email protected]>

modules/app_dash.py

@@ -108,8 +108,24 @@ def find_dashcam_partition():
 
 
 def mount_device(device_path, mount_point=DEFAULT_MOUNT_POINT):
-    """Mount device_path read-only at mount_point. Returns True on success."""
+    """Mount device_path read-only at mount_point. Returns True on success.
-    os.makedirs(mount_point, exist_ok=True)
+
+    The app runs as an unprivileged user while /mnt is root-owned, so the
+    mount point directory itself has to be created via sudo too (not just
+    the mount call) - first real-hardware test surfaced this as a plain
+    PermissionError from a bare os.makedirs().
+    """
+    try:
+        subprocess.run(
+            ["sudo", "mkdir", "-p", mount_point],
+            capture_output=True,
+            text=True,
+            check=True,
+        )
+    except subprocess.CalledProcessError as e:
+        print(f"Failed to create mount point {mount_point}: {e.stderr.strip()}")
+        return False
+
     try:
         subprocess.run(
             ["sudo", "mount", "-o", "ro", device_path, mount_point],