fix(intents): register calendar intent filters so Calendula can be the default calendar (#9)

Calendula didn't declare the intent filters launchers and the system use for
calendar actions, so it never appeared in the "default calendar app" chooser —
on every platform, not just GrapheneOS (issue #9). Android exposes no API for an
app to set itself default, so registering these filters is the only way users can
pick it from the system picker.

Adds to MainActivity:
- MAIN + APP_CALENDAR — the "open the calendar app" action the OS/launchers use.
- VIEW on content://com.android.calendar/time/<epochMillis> and the time/epoch
  mime type — a launcher/clock date tap. The provider's time Uri is parsed into a
  LocalDate and opened on the day view, rooted over the default home view (a new
  sourceless WidgetNavRequest.OpenDate). The .ics import path now ignores the
  calendar provider host so a date tap isn't mistaken for a file to import.

Bumps to 2.11.1.

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

app/build.gradle.kts

@@ -28,8 +28,8 @@ android {
         // which builds this version and then creates the matching vX.Y.Z tag +
         // release itself (versionCode is pinned to MAJOR*10000 + MINOR*100 +
         // PATCH from versionName, e.g. 2.7.2 -> 20702). See docs/RELEASING.md.
-        versionCode = 21100
-        versionName = "2.11.0"
+        versionCode = 21101
+        versionName = "2.11.1"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }