Add 'Clear all' button to wipe the tracker list

Trash action in the top bar (shown when the list is non-empty) clears all tracker rows + sighting history via repo.clearAll(). Devices re-populate as they're re-detected; learned baseline places are kept. Release 0.1.4.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0187UiEtasyowhEBYs6s9iF5

app/build.gradle.kts

@@ -13,8 +13,8 @@ android {
         applicationId = "org.soulstone.vigil"
         minSdk = 26
         targetSdk = 35
-        versionCode = 4
-        versionName = "0.1.3"
+        versionCode = 5
+        versionName = "0.1.4"
     }
 
     // Fixed debug keystore committed to the repo (a debug key is non-secret — its