feat: add standalone Discord Rich Presence controller app

rp-app/.gitignore

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+node_modules/
+dist/
+.DS_Store
+*.log

rp-app/README.md

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+# Discord Rich Presence Controller
+
+A simple Electron app to set custom Discord Rich Presence status.
+
+## Setup
+
+1. Install dependencies:
+   ```bash
+   npm install
+   ```
+
+2. Run the app:
+   ```bash
+   npm start
+   ```
+
+## Usage
+
+1. **Get a Discord Application ID**:
+   - Go to [Discord Developer Portal](https://discord.com/developers/applications)
+   - Create a new application (or use an existing one)
+   - Copy the "Application ID" from the General Information page
+
+2. **Set up Rich Presence Assets** (optional):
+   - In your Discord application, go to "Rich Presence" → "Art Assets"
+   - Upload images you want to use for large/small icons
+   - Note the asset names for use in the app
+
+3. **Connect and Customize**:
+   - Paste your Application ID in the app
+   - Click "Connect"
+   - Fill in the fields you want to display
+   - Click "Update Presence"
+
+## Fields
+
+| Field | Description | Max Length |
+|-------|-------------|------------|
+| Details | First line of text | 128 chars |
+| State | Second line of text | 128 chars |
+| Large Image | Asset name or image URL | - |
+| Large Image Text | Hover text for large image | 128 chars |
+| Small Image | Asset name or image URL | - |
+| Small Image Text | Hover text for small image | 128 chars |
+| Button 1/2 Label | Button text | 32 chars |
+| Button 1/2 URL | Button link | Valid URL |
+
+## Activity Types
+
+- **Playing** - "Playing {details}"
+- **Streaming** - "Streaming {details}"
+- **Listening** - "Listening to {details}"
+- **Watching** - "Watching {details}"
+- **Competing** - "Competing in {details}"
+
+## Timestamps
+
+- **Elapsed**: Shows "XX:XX elapsed"
+- **Remaining**: Shows "XX:XX left" (requires duration)
+
+## Notes
+
+- Discord must be running for Rich Presence to work
+- Buttons are only visible to other users (not yourself)
+- Image URLs must be publicly accessible HTTPS URLs
+- Changes may take a few seconds to appear in Discord
+
+## Architecture
+
+This app follows the same Discord RPC implementation pattern as [YouTube Music Desktop](https://github.com/pear-devs/pear-desktop):
+
+```
+src/
+├── main/
+│   ├── index.js          # Electron main process
+│   ├── discord-service.js # Discord RPC service
+│   ├── timer-manager.js   # Timer management
+│   └── constants.js       # Constants
+├── renderer/
+│   ├── index.html        # UI
+│   ├── styles.css        # Styles
+│   └── renderer.js       # UI logic
+└── preload.js            # IPC bridge
+```
+
+## License
+
+MIT

rp-app/package.json

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+{
+  "name": "rp",
+  "version": "1.0.0",
+  "description": "Custom Discord Rich Presence Controller",
+  "main": "src/main/index.js",
+  "scripts": {
+    "start": "electron .",
+    "dev": "electron ."
+  },
+  "author": "",
+  "license": "MIT",
+  "devDependencies": {
+    "electron": "^33.0.0"
+  },
+  "dependencies": {
+    "@xhayper/discord-rpc": "^1.3.0"
+  }
+}

rp-app/src/main/constants.js

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+/**
+ * Enum for keys used in TimerManager.
+ */
+const TimerKey = {
+  DiscordConnectRetry: 'discordConnectRetry',
+};
+
+module.exports = { TimerKey };