Add setting to disable overlay while keeping BLE transmission active

[Copilot]

This PR adds a new configuration option that allows users to disable the overlay display while maintaining BLE transmission functionality, addressing the need for BLE-only operation without the visual overlay.

Changes Made

New Configuration Setting

• Added ShowOverlay preference to ConfigurationRepository with proper persistence
• Exposed the setting through ConfigurationViewModel with appropriate handlers
• Added "Show overlay on screen?" checkbox to the configuration UI

Smart UI Behavior

• Button text dynamically changes from "Click here to start the overlay" to "Start service (BLE only)" when overlay is disabled
• Added informational message "ℹ️ BLE transmission is active without overlay display" when BLE is enabled but overlay is disabled
• Maintains clear visual feedback about the current operational mode

Service Optimization

• Modified OverlayService to conditionally skip overlay creation when the setting is disabled
• Ensures BLE functionality remains completely independent through the application-level sensor interface
• Prevents unnecessary resource allocation when overlay is not needed

User Scenarios

Default Behavior: Both overlay and BLE enabled (unchanged from original)

[✓] Show overlay on screen?
[✓] Enable BLE TX (Transmission)?
[Click here to start the overlay]

BLE-Only Mode: Overlay disabled, BLE enabled (new functionality)

[ ] Show overlay on screen?
[✓] Enable BLE TX (Transmission)?
ℹ️ BLE transmission is active without overlay display
[Start service (BLE only)]

This implementation provides exactly what users requested: the ability to use Grupetto's BLE transmission features without displaying the overlay interface, perfect for scenarios where users only need the bike data broadcasting capability.

Fixes #5.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.google.com
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED -Xmx2048m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-8.5-bin/5t9huq95ubn472n8rpzujfbqh/gradle-8.5/lib/gradle-launcher-8.5.jar -javaagent:/home/REDACTED/.gradle/wrapper/dists/gradle-8.5-bin/5t9huq95ubn472n8rpzujfbqh/gradle-8.5/lib/agents/gradle-instrumentation-agent-8.5.jar org.gradle.launcher.daemon.bootstrap.GradleDaemon 8.5 (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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