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/appwidget_info_month.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
+    android:minWidth="250dp"
+    android:minHeight="180dp"
+    android:targetCellWidth="4"
+    android:targetCellHeight="4"
+    android:minResizeWidth="180dp"
+    android:minResizeHeight="150dp"
+    android:resizeMode="horizontal|vertical"
+    android:widgetCategory="home_screen"
+    android:description="@string/widget_month_label"
+    android:updatePeriodMillis="1800000"
+    android:previewLayout="@layout/widget_preview_month"
+    android:initialLayout="@layout/glance_default_loading_layout" />