feat: persist led config on debian startup

test_led_panel.py

@@ -29,7 +29,9 @@ def main():
         (d / 'trigger').write_text('[none] timer')
         (d / 'delay_on').write_text('500')
         (d / 'delay_off').write_text('500')
+        config_path = root / 'config.json'
         led_panel.LED_ROOT = root
+        led_panel.CONFIG_PATH = config_path
         httpd = ThreadingHTTPServer(('127.0.0.1', 0), Handler)
         port = httpd.server_address[1]
         t = threading.Thread(target=httpd.serve_forever, daemon=True)
@@ -44,7 +46,19 @@ def main():
             assert (d / 'trigger').read_text() == 'timer'
             delay = req(port, '/api/delay', {'name':'blue:wan','field':'delay_on','value':123})
             assert delay['ok'] and (d / 'delay_on').read_text() == '123'
-            print('OK: API write regression passed')
+            saved = req(port, '/api/save', {'name':'blue:wan'})
+            assert saved['ok'] and config_path.exists()
+            cfg = json.loads(config_path.read_text())
+            assert cfg['leds']['blue:wan']['delay_on'] == 123
+            # Simulate reboot/default reset, then apply persisted config.
+            (d / 'brightness').write_text('0')
+            (d / 'trigger').write_text('[none] timer')
+            (d / 'delay_on').write_text('500')
+            applied = req(port, '/api/apply-saved', {})
+            assert applied['ok'] and applied['applied'] == 1
+            assert (d / 'brightness').read_text() == '1'
+            assert (d / 'delay_on').read_text() == '123'
+            print('OK: API write + persistence regression passed')
         finally:
             httpd.shutdown()