release: cut v2.5.0 — home-screen widgets, agenda, jump-to-date, quick actions

Bundles the unreleased Tier 2/3 work into one release:

- Home-screen widgets (Glance): an "Upcoming" agenda widget and a month-grid
  widget, both reusing the in-app grouping/layout (groupAgendaDays,
  layoutMonthWeeks) via a Hilt WidgetEntryPoint, honouring hidden-calendar
  filters and refreshing on PROVIDER_CHANGED / date rollover.
- App shortcut: launcher long-press "New event", routed through the shared
  WidgetNavRequest.Create channel into the create-event form.
- Agenda view and jump-to-date (already merged via #3/#4) are documented here
  as part of the shipped version.

Bumps versionCode 20500 / versionName 2.5.0, moves the CHANGELOG Unreleased
section under [2.5.0], updates ROADMAP/STATE, and adds EN+DE strings.

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

app/src/main/res/xml/shortcuts.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Launcher long-press shortcuts. The intent fires a custom action that
+     MainActivity (singleTop) consumes to open the create-event form on today;
+     see MainActivity.ACTION_NEW_EVENT. -->
+<shortcuts xmlns:android="http://schemas.android.com/apk/res/android">
+    <shortcut
+        android:shortcutId="new_event"
+        android:enabled="true"
+        android:icon="@drawable/ic_shortcut_new_event"
+        android:shortcutShortLabel="@string/shortcut_new_event_short"
+        android:shortcutLongLabel="@string/shortcut_new_event_long">
+        <intent
+            android:action="de.jeanlucmakiola.calendula.action.NEW_EVENT"
+            android:targetPackage="de.jeanlucmakiola.calendula"
+            android:targetClass="de.jeanlucmakiola.calendula.MainActivity" />
+    </shortcut>
+</shortcuts>