Wrap createDocuments in skipDuplicates for idempotent re-imports

CSV / JSON / appwrite-to-appwrite imports that re-run on the same
batch (e.g. user re-uploads the same file, or a worker retries a
failed chunk) currently throw DuplicateException and abort the whole
batch. Wrap the row-buffer flush in the new skipDuplicates() scope
guard so duplicate-by-id rows are silently no-op'd at the adapter
layer (INSERT IGNORE / ON CONFLICT DO NOTHING / $setOnInsert), letting
the rest of the batch proceed.

The existing skipRelationshipsExistCheck() wrapper is preserved
(FK-target guard); skipDuplicates composes around it.

Feature-branch note: depends on utopia-php/database's skipDuplicates()
scope guard from PR utopia-php/database#852. composer.json is
temporarily pinned to dev-csv-import-upsert-v2 with a 5.99.0 alias so
composer can resolve the 5.* constraint transitively. Must be reset
to the proper release version (^5.X.Y) once PR #852 merges and
utopia-php/database ships.

Author: premtsd-code

composer.json

@@ -4,7 +4,8 @@
     "type": "library",
     "keywords": ["php", "framework", "upf", "utopia", "migration"],
     "license": "MIT",
-    "minimum-stability": "stable",
+    "minimum-stability": "dev",
+    "prefer-stable": true,
     "autoload": {
         "psr-4": {
             "Utopia\\Migration\\": "src/Migration"
@@ -26,7 +27,7 @@
         "ext-curl": "*",
         "ext-openssl": "*",
         "appwrite/appwrite": "19.*",
-        "utopia-php/database": "5.*",
+        "utopia-php/database": "dev-csv-import-upsert-v2 as 5.99.0",
         "utopia-php/storage": "1.0.*",
         "utopia-php/dsn": "0.2.*",
         "halaxa/json-machine": "^1.2"