pscand-cli: error when there are no scanners configured

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: Id4e5a2ffc70efb10ba37c0b203a0ac166a6a6964

config/pscand.toml

@@ -42,12 +42,8 @@ interval_secs = 30  # Battery status changes slowly
 enabled = true
 interval_secs = 5
 
-# Example: Disable a scanner
-[scanners.system]
-enabled = false
-
 # Example: Custom scanner with extra parameters
-[scanners.custom]
-enabled = true
-interval_secs = 60
-extra = { custom_param = "value", threshold = 100 }
+# [scanners.custom]
+# enabled = true
+# interval_secs = 60
+# extra = { custom_param = "value", threshold = 100 }