Refresh the shared snapshot in the background so widgets stop going stale

publishWidgetSnapshot() only ever ran from a user action, so an event created
on the web or on Android did not reach the widgets until the app was opened
again. A BGAppRefreshTask now republishes without the foreground.

The two keys this needs are arrays, which Xcode does not expose as
INFOPLIST_KEY_ build settings — verified by building and inspecting the
result. Hence a partial Calendarr-Info.plist that generation merges into. It
sits at the project root rather than inside the target folder: that folder is
a synchronized group, which would also copy the file as a resource and collide
with the processed one.

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

Calendarr-Info.plist

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>BGTaskSchedulerPermittedIdentifiers</key>
+	<array>
+		<string>com.scarriffleservices.calendarr.ios.refresh</string>
+	</array>
+	<key>UIBackgroundModes</key>
+	<array>
+		<string>fetch</string>
+	</array>
+</dict>
+</plist>