Add URL scheme support for external trigger integration

Register snippingtool:// URL scheme so external tools (Logitech Options,
Shortcuts, Stream Deck) can trigger specific capture modes directly.
Adds AppDelegate for reliable URL handling in MenuBarExtra-only apps.

Supported URLs:
  snippingtool://fullscreen
  snippingtool://window
  snippingtool://region

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

project.yml

@@ -18,6 +18,10 @@ targets:
         CFBundleName: Snipping Tool
         LSUIElement: true
         NSHumanReadableCopyright: "Copyright © 2026"
+        CFBundleURLTypes:
+          - CFBundleURLName: it.wende.snippingtool
+            CFBundleURLSchemes:
+              - snippingtool
     settings:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: it.wende.snippingtool