refactor(crash): draw crash capture + report UI from floret-kit core-crash

Replace the app-local crash machinery (CrashReporter, CrashReportDialog,
CrashReportSubmit) with floret-kit's core-crash. The kit version is the same
privacy-respecting, on-device, no-network design (clipboard + prefilled issue
URL via ACTION_VIEW), parameterised by a CrashConfig: app label + the
issue-tracker URLs, supplied once at install() in CalendulaApp.

- CrashReportActivity stays app-local (thin standalone surface) but now imports
  the kit's CrashReporter/CrashReportDialog/submitCrashReport.
- buildCrashReport moved to the kit and gained an appLabel parameter; the
  privacy-allowlist test is repointed to the kit API (still pins Calendula's
  exact six-line header — no identifiers, no calendar content).
- Calendula keeps its own crash strings (incl. German + "calendar content"
  wording) as resource overrides, converted to the kit's %1$s app-label /
  two-arg body-template arity so the shared code formats them correctly.

Compile + unit tests + lintDebug green.

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

app/build.gradle.kts

@@ -161,6 +161,7 @@ dependencies {
     implementation(libs.kotlinx.datetime)
     implementation("de.jeanlucmakiola.floret:core-time")
     implementation("de.jeanlucmakiola.floret:core-locale")
+    implementation("de.jeanlucmakiola.floret:core-crash")
     implementation(libs.kotlinx.coroutines.core)
 
     debugImplementation(libs.androidx.ui.tooling)