feat: prioritize Bluetooth sensor data over GPS

- Restructured sensor logic to give absolute priority to Bluetooth sensors, largely ignoring GPS data for distance and speed calculations.
- Implemented downstream UI expansions, custom recording layouts, and new settings to reflect and control the new sensor-first flow.
- Added MediaNotificationListenerService and integrated media playback tracking within statistics.
- Modified VoiceAnnouncementUtils to harmonize announcements with the updated architecture.
- Added 'About This Fork' section to the README.

Note: These modifications were co-created with Antigravity AI.

README.md

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+## ⚠️ About This Fork
+
+This repository is a customized fork of the official OpenTracks application. 
+
+**Core Purpose:** 
+The primary goal of this fork is to fundamentally change how Bluetooth sensors are prioritized over GPS data. In this modified version, Bluetooth sensor data is given absolute priority and actively ignores/overrides GPS signals in most scenarios. This ensures that cadence, speed, and distance measurements strictly rely on hardware sensors rather than falling back to or being averaged with GPS data.
+
+**Consequential Changes:**
+As a direct result of these sensor priority changes, several downstream modifications were implemented to support the new data flow:
+* **UI & Settings:** Expanded settings menus and customized recording layouts to better expose the raw sensor data and give the user finer control.
+* **Media & Voice Announcements:** Integrated media playback controls directly into the statistics view and overhauled voice announcements to handle audio focus and integrate with the new sensor-first approach.
+
 ## Screenshots
 
 <div>