feat(todo): reminders on the device, Upcoming's week strip, the task pane and search (ADR 0033, D2, D5, D8)

A task with a time takes reminders, minutes before it, in its sealed
payload; each device plans the coming ones whenever the tasks change and
schedules them with the system through flutter_local_notifications
(Android, iOS, macOS, Windows; on Linux the running app shows them), at
the minute where Android allows exact alarms. Notifying is asked for
when a task first gets a reminder; signing out or switching person
cancels them. Upcoming gets its week strip: the month opening
Material's calendar, the weeks before and after, a dot under each day
with tasks; a day picked scrolls the agenda to it, and scrolling moves
the strip along. From expanded windows on, a task opens in a pane
beside the list rather than in a dialog. Search, from every tab's app
bar, finds projects by name and tasks by every word typed, in their
title, description or labels, whatever the case and accents, on the
device alone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_flutter/android/app/build.gradle.kts

@@ -10,6 +10,9 @@ android {
     ndkVersion = flutter.ndkVersion
 
     compileOptions {
+        // flutter_local_notifications' scheduling uses java.time, which
+        // Android before 8 lacks (ADR 0033, D5).
+        isCoreLibraryDesugaringEnabled = true
         sourceCompatibility = JavaVersion.VERSION_17
         targetCompatibility = JavaVersion.VERSION_17
     }
@@ -47,3 +50,7 @@ kotlin {
 flutter {
     source = "../.."
 }
+
+dependencies {
+    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
+}

apps/todo/halkyon_todo_flutter/android/app/src/main/AndroidManifest.xml

@@ -2,6 +2,12 @@
     <!-- The app talks to its instance: release builds need this too (Flutter's
          template grants it to debug and profile builds only). -->
     <uses-permission android:name="android.permission.INTERNET"/>
+    <!-- Tasks' reminders (ADR 0033, D5): shown (POST_NOTIFICATIONS comes with
+         flutter_local_notifications), scheduled again after a restart, and at
+         the minute where the person allows exact alarms (Android 14 leaves
+         them off; without, Android may bring a reminder a few minutes late). -->
+    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
+    <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM"/>
     <application
         android:label="Halkyon Todo"
         android:name="${applicationName}"
@@ -40,6 +46,17 @@
                 <data android:scheme="app.halkyon.todo" />
             </intent-filter>
         </activity>
+        <!-- Shows the reminders scheduled, and schedules them again after a
+             restart or an update (flutter_local_notifications). -->
+        <receiver android:exported="false" android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationReceiver" />
+        <receiver android:exported="false" android:name="com.dexterous.flutterlocalnotifications.ScheduledNotificationBootReceiver">
+            <intent-filter>
+                <action android:name="android.intent.action.BOOT_COMPLETED"/>
+                <action android:name="android.intent.action.MY_PACKAGE_REPLACED"/>
+                <action android:name="android.intent.action.QUICKBOOT_POWERON" />
+                <action android:name="com.htc.intent.action.QUICKBOOT_POWERON"/>
+            </intent-filter>
+        </receiver>
         <!-- Don't delete the meta-data below.
              This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
         <meta-data