PWR: add optional polling mode

enable watch_polling/"Use polling" if the usual PWR monitoring doesn't
work for you (likely if you're using a network mount (SMB/NFS) or
anything with FUSE.

config/config-base.yaml

@@ -1179,6 +1179,13 @@ sections:
     type: text
     value: /path/to/jellyfin
     description: Path to the folder Jellyfin puts password-reset files.
+  - setting: watch_polling
+    name: Use polling
+    requires_restart: true
+    depends_true: watch_directory 
+    type: bool
+    value: false
+    description: Use if mounting over network (NFS/SMB/SFTP). Watch the Jellyfin directory by checking periodically, rather than using OS APIs.
   - setting: link_reset
     name: Use reset link instead of PIN (Required for Ombi)
     requires_restart: true