feat(storage): add Apple iCloud Drive storage provider

Add iCloud Drive as a new storage destination using the pyicloud library.
Includes upload task, configuration, user integration handler, provider
status, onboarding support, and comprehensive tests.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/models.py

@@ -505,6 +505,7 @@ class IntegrationType:
     EMAIL = "EMAIL"
     PAPERLESS = "PAPERLESS"
     RCLONE = "RCLONE"
+    ICLOUD = "ICLOUD"
 
     ALL = {
         IMAP,
@@ -521,6 +522,7 @@ class IntegrationType:
         EMAIL,
         PAPERLESS,
         RCLONE,
+        ICLOUD,
     }