feat: replace script args with typed named parameters

- Change execute_script API from positional args list to named params dict
- Update service schema, API client, and constants
- Add execute_script service documentation to README

README.md

@@ -103,6 +103,48 @@ Button entities for each script defined on your Media Server:
 - Shutdown, restart, sleep, hibernate
 - Custom scripts
 
+### Execute Script Service
+
+Call `remote_media_player.execute_script` to run any server-defined script with typed parameters:
+
+```yaml
+service: remote_media_player.execute_script
+data:
+  script_name: set_brightness
+  params:
+    level: 75
+    monitor: primary
+```
+
+Parameters are validated against the script's schema on the server. Scripts define their parameters in `config.yaml`:
+
+```yaml
+scripts:
+  set_brightness:
+    command: "python set_brightness.py"
+    label: "Set Brightness"
+    icon: "mdi:brightness-6"
+    timeout: 10
+    parameters:
+      level:
+        type: integer
+        required: true
+        min: 0
+        max: 100
+        description: "Brightness level (0-100)"
+      monitor:
+        type: select
+        options: ["primary", "secondary", "all"]
+        default: "primary"
+        description: "Target monitor"
+```
+
+Supported parameter types: `string`, `integer`, `float`, `boolean`, `select`.
+
+Parameters are passed to scripts as environment variables prefixed with `SCRIPT_PARAM_` (e.g., `SCRIPT_PARAM_LEVEL=75`, `SCRIPT_PARAM_MONITOR=primary`).
+
+Scripts without parameters work as before — just omit `params`.
+
 ## Example Lovelace Card
 
 ```yaml