v0.2.3: true ticking countdown via a tiny native module (no deps)

Replaces the static status notification with a native Android chronometer that
counts DOWN to the session end — the system ticks it every second with zero app
CPU/battery, visible without opening the app.

- modules/bbp-notify: a ~50-line local Expo module using only NotificationCompat
  (setWhen + setUsesChronometer + setChronometerCountDown + ongoing). Zero
  third-party dependencies, no Firebase — fits the de-Googled ethos. Verified:
  autolinks + Kotlin compiles.
- sessionStatus.ts uses it when present, else falls back to the expo-notifications
  static expiry-time notification.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/modules/bbp-notify/index.ts

@@ -0,0 +1,31 @@
+import { Platform } from 'react-native';
+import { requireOptionalNativeModule } from 'expo-modules-core';
+
+interface BbpNotifyNative {
+  /** Post/replace an ongoing notification with a native chronometer counting down to endTimeMillis. */
+  showCountdown(title: string, body: string, endTimeMillis: number): Promise<void>;
+  /** Remove the countdown notification. */
+  clear(): Promise<void>;
+}
+
+// Android-only, and only present in a build that includes the native module
+// (returns null in Expo Go / other platforms — callers degrade gracefully).
+const native =
+  Platform.OS === 'android'
+    ? (requireOptionalNativeModule('BbpNotify') as BbpNotifyNative | null)
+    : null;
+
+/** True when the native ticking-countdown module is available. */
+export const hasNativeCountdown = native != null;
+
+export async function showCountdown(
+  title: string,
+  body: string,
+  endTimeMillis: number,
+): Promise<void> {
+  await native?.showCountdown(title, body, endTimeMillis);
+}
+
+export async function clearCountdown(): Promise<void> {
+  await native?.clear();
+}