Feature: Spotify Integration for Alarm Ringtones

### Description

Currently, Ultimate Alarm Clock supports custom ringtones, but many users prefer waking up to their favorite Spotify playlists or songs.

## Proposed Solution

Integrate Spotify as an alarm sound option allowing users to:

- Select Spotify playlists
- Select Spotify songs
- Launch Spotify on alarm trigger
- Fallback to default ringtone if playback fails

## Implementation Plan

- Use Spotify Android SDK or deep linking
- Authenticate user
- Launch Spotify on alarm trigger
- Implement fallback mechanism

## Benefits

- Better user experience
- Modern alarm functionality
- High real-world value

I would like to work on this feature as part of my GSoC 2026 contribution.

### Screenshots

_No response_