Add callbacks support for all media actions

- Add CallbackConfig model for callback scripts
- Add callbacks section to config for optional command execution
- Add turn_on/turn_off/toggle endpoints (callback-only)
- Add callbacks for all media actions (play, pause, stop, next, previous, volume, mute, seek)
- Update README with callbacks documentation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -164,6 +164,9 @@ All control endpoints require authentication and return `{"success": true}` on s
 | `/api/media/volume` | POST | `{"volume": 75}` | Set volume (0-100) |
 | `/api/media/mute` | POST | - | Toggle mute |
 | `/api/media/seek` | POST | `{"position": 60.0}` | Seek to position (seconds) |
+| `/api/media/turn_on` | POST | - | Execute on_turn_on callback |
+| `/api/media/turn_off` | POST | - | Execute on_turn_off callback |
+| `/api/media/toggle` | POST | - | Execute on_toggle callback |
 
 ### Script Execution
 
@@ -263,6 +266,95 @@ Script configuration options:
 | `working_dir` | No | Working directory for the command |
 | `shell` | No | Run in shell (default: true) |
 
+### Configuring Callbacks
+
+Callbacks are optional commands executed after media actions. Add them in your `config.yaml`:
+
+```yaml
+callbacks:
+  # Media control callbacks (run after successful action)
+  on_play:
+    command: "echo Play triggered"
+    timeout: 10
+    shell: true
+
+  on_pause:
+    command: "echo Pause triggered"
+    timeout: 10
+    shell: true
+
+  on_stop:
+    command: "echo Stop triggered"
+    timeout: 10
+    shell: true
+
+  on_next:
+    command: "echo Next track"
+    timeout: 10
+    shell: true
+
+  on_previous:
+    command: "echo Previous track"
+    timeout: 10
+    shell: true
+
+  on_volume:
+    command: "echo Volume changed"
+    timeout: 10
+    shell: true
+
+  on_mute:
+    command: "echo Mute toggled"
+    timeout: 10
+    shell: true
+
+  on_seek:
+    command: "echo Seek triggered"
+    timeout: 10
+    shell: true
+
+  # Turn on/off/toggle (callback-only actions, no default behavior)
+  on_turn_on:
+    command: "echo PC turned on"
+    timeout: 10
+    shell: true
+
+  on_turn_off:
+    command: "rundll32.exe user32.dll,LockWorkStation"
+    timeout: 5
+    shell: true
+
+  on_toggle:
+    command: "echo Toggle triggered"
+    timeout: 10
+    shell: true
+```
+
+Available callbacks:
+
+| Callback | Triggered by | Description |
+|----------|--------------|-------------|
+| `on_play` | `/api/media/play` | After play succeeds |
+| `on_pause` | `/api/media/pause` | After pause succeeds |
+| `on_stop` | `/api/media/stop` | After stop succeeds |
+| `on_next` | `/api/media/next` | After next track succeeds |
+| `on_previous` | `/api/media/previous` | After previous track succeeds |
+| `on_volume` | `/api/media/volume` | After volume change succeeds |
+| `on_mute` | `/api/media/mute` | After mute toggle |
+| `on_seek` | `/api/media/seek` | After seek succeeds |
+| `on_turn_on` | `/api/media/turn_on` | Callback-only action |
+| `on_turn_off` | `/api/media/turn_off` | Callback-only action |
+| `on_toggle` | `/api/media/toggle` | Callback-only action |
+
+Callback configuration options:
+
+| Field | Required | Description |
+|-------|----------|-------------|
+| `command` | Yes | Command to execute |
+| `timeout` | No | Execution timeout in seconds (default: 30, max: 300) |
+| `working_dir` | No | Working directory for the command |
+| `shell` | No | Run in shell (default: true) |
+
 ## Running as a Service
 
 ### Windows Task Scheduler (Recommended)