✨(import) add import modal

Synchronous for now, can be offloaded to worker later.

Also lint the codebase

docker/sabredav/composer.json

@@ -2,9 +2,15 @@
     "name": "calendars/sabredav-server",
     "description": "sabre/dav CalDAV server for calendars",
     "type": "project",
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/sylvinus/dav"
+        }
+    ],
     "require": {
         "php": ">=8.1",
-        "sabre/dav": "^4.5",
+        "sabre/dav": "dev-master",
         "ext-pdo": "*",
         "ext-pdo_pgsql": "*"
     },