docs: add plugin handoff for Android 6.0 (API 23) ZoneId fix

Add doc/plugin-feedback-android-6-api23-zoneid-fix.md for the
daily-notification-plugin repo: replace java.time.ZoneId with
TimeZone.getDefault().id so the plugin runs on API 23 without
affecting behavior on API 26+.

doc/plugin-feedback-android-6-api23-zoneid-fix.md

@@ -0,0 +1,71 @@
+# Plugin fix: Android 6.0 (API 23) compatibility — replace java.time.ZoneId with TimeZone
+
+**Date:** 2026-02-27  
+**Target repo:** daily-notification-plugin  
+**Consuming app:** crowd-funder-for-time-pwa (TimeSafari)  
+**Platform:** Android
+
+---
+
+## Summary
+
+On Android 6.0 (API 23), the plugin crashes at runtime when scheduling a daily notification because it uses `java.time.ZoneId`, which is only available from **API 26**. Replacing that with `java.util.TimeZone.getDefault().getID()` restores compatibility with API 23 and has **no functional impact** on API 26+ (same timezone ID string, same behavior).
+
+---
+
+## Problem
+
+- **File:** `android/src/main/java/com/timesafari/dailynotification/NotifyReceiver.kt`
+- **Approximate location:** inside `scheduleExactNotification()`, when building `NotificationContentEntity` (around line 260).
+
+The code uses:
+
+```kotlin
+java.time.ZoneId.systemDefault().id
+```
+
+On API 23 this causes a runtime failure (e.g. `NoClassDefFoundError`) when the scheduling path runs, because `java.time` was added to Android only in API 26 (Oreo).
+
+---
+
+## Required change
+
+Replace the `java.time` call with the API-1–compatible equivalent.
+
+**Before:**
+
+```kotlin
+java.time.ZoneId.systemDefault().id
+```
+
+**After:**
+
+```kotlin
+java.util.TimeZone.getDefault().id
+```
+
+Use this in the same place where `NotificationContentEntity` is constructed (the parameter that stores the system timezone ID string). No other code changes are needed.
+
+---
+
+## Why this is safe on newer Android
+
+- Both `ZoneId.systemDefault().id` and `TimeZone.getDefault().id` refer to the **same** system default timezone and return the **same** IANA timezone ID string (e.g. `"America/Los_Angeles"`, `"Europe/London"`).
+- Any downstream logic that reads this string (e.g. for display or next-run calculation) behaves identically on API 26+.
+- No change to data format or semantics; this is a backward-compatible drop-in replacement.
+
+---
+
+## Verification
+
+1. **Build:** From a consuming app (e.g. crowd-funder-for-time-pwa) with `minSdkVersion = 23`, run a full Android build including the plugin. No compilation errors.
+2. **Runtime on API 23:** On an Android 6.0 device or emulator, enable daily notifications and schedule a time. The app should not crash; the notification should be scheduled and (after the delay) fire.
+3. **Runtime on API 26+:** Confirm scheduling and delivery still work as before on Android 8+.
+
+---
+
+## Context (consuming app)
+
+- App and plugin both declare `minSdkVersion = 23` (Android 6.0). AlarmManager, permissions, and notification paths in the plugin are already API-23 safe; this `java.time` usage is the only blocker for running on Android 6.0 devices.
+
+Use this document when applying the fix in the **daily-notification-plugin** repo (e.g. in Cursor). After changing the plugin, update the consuming app’s dependency (e.g. `npm update @timesafari/daily-notification-plugin` or point at the fixed commit), then `npx cap sync android` and rebuild.