Survivor side (2/4): alert history + evidence export (report + GPX)

- Room 'alerts' table records each new ALERTING event (ecosystem, time, distinct places, peak RSSI, location).
- History screen: log of past alerts + a one-tap Export that shares a timestamped text report and a GPX of every geotagged sighting (open in a maps app). Files written to cache and shared via FileProvider — no network.
- History icon added to the header.
Release 0.1.9.

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 = 9
-        versionName = "0.1.8"
+        versionCode = 10
+        versionName = "0.1.9"
     }
 
     // Fixed debug keystore committed to the repo (a debug key is non-secret — its