feat(intents): open .ics/.vcs handed over as application/octet-stream (#74)

Mail clients, browsers and file managers frequently label a calendar
attachment as a generic download (application/octet-stream) rather than
text/calendar, so the MIME-typed VIEW filter missed them. Add a dedicated
filter that matches those by .ics/.vcs extension via pathPattern — kept
separate so the path constraint can't narrow the reliable MIME-typed filter.
The import handler already ignores the declared MIME, so a let-through file
imports normally. Best-effort: reliable for file:// and content:// whose path
carries the name; nameless content:// URIs still fall back to the MIME filter.

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

CHANGELOG.md

@@ -38,6 +38,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   didn't advertise — so it was left out of the chooser, and if it was your only
   calendar app the save silently did nothing. It now accepts that form, plus the
   `INSERT_OR_EDIT` action, and opens the new event prefilled for review ([#74]).
+- Opening a `.ics`/`.vcs` file now works even when another app hands it over
+  mislabelled as a generic download (`application/octet-stream`), as some mail
+  clients, browsers and file managers do — Calendula recognises it by its file
+  extension instead of relying on the declared type ([#74]).
 
 ## [2.16.0] — 2026-07-17