fix(ui): fine-tune plugins config form (#4916)

* fix(ui): use stock array renderer for plugins config form

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(plugins): enforce minimum user tokens and require users field

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(ui): simplify error handling in control state hook

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(ui): remove "None" MenuItem from OutlinedEnumControl

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(ui): enhance error handling by returning field info and path in validation errors

Signed-off-by: Deluan <deluan@navidrome.org>

* fix(ui): update OutlinedEnumControl to handle empty values and remove "None" option when required

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/examples/discord-rich-presence-rs/manifest.json

@@ -42,7 +42,7 @@
           "type": "array",
           "title": "User Tokens",
           "description": "Discord tokens for each Navidrome user. WARNING: Store tokens securely!",
-          "default": [{}],
+          "minItems": 1,
           "items": {
             "type": "object",
             "properties": {
@@ -63,7 +63,7 @@
           }
         }
       },
-      "required": ["clientid"]
+      "required": ["clientid", "users"]
     },
     "uiSchema": {
       "type": "VerticalLayout",