release: cut v1.0.0 — first public release

Version bumped to 1.0.0 / 7. No code changes beyond the version — 1.0.0 is the
accumulated v0.1 → v0.6 work (all V1 screens, full event read, filter, settings,
onboarding polish) declared release-ready. CHANGELOG [1.0.0] summarises the
shipped feature set; ROADMAP/STATE mark V1 complete.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/build.gradle.kts

@@ -23,8 +23,8 @@ android {
         applicationId = "de.jeanlucmakiola.calendula"
         minSdk = 29
         targetSdk = 36
-        versionCode = 6
-        versionName = "0.6.0"
+        versionCode = 7
+        versionName = "1.0.0"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }