Add relay enable toggles to WebUI

docs/API.md

@@ -396,7 +396,7 @@ Fields:
 |---|---:|---|
 | `id` | Yes | `relay_1` or `relay_2` |
 | `name` | No | User display name |
-| `enabled` | No | Configured enabled state |
+| `enabled` | No | Configured enabled state. When set to `false`, the relay output is forced OFF and future relay control requests are rejected with `relay_disabled`. |
 
 Returns the updated config.
 

docs/CONFIGURATION.md

@@ -69,6 +69,8 @@ HTTP endpoint:
 
     POST /api/v1/config/relay
 
+Disabled relays are forced OFF immediately, hidden from normal dashboard controls, and protected from `/api/v1/relay/set` commands until re-enabled.
+
 ## Temperature Sensor Configuration
 
 Temperature sensors use generic firmware IDs: