Resolved issue where uploads to MSM shared upload directories showed a post_max_size error and left files behind when validation failed - #5445

Upload directories created with Share Upload Directory on all sites are stored with site_id 0. The modern File models already look them up with site_id IN (0, current) (Service/File/Upload::uploadTo(), the file and file grid fieldtypes, the filepicker). The legacy File_upload_preferences_model::get_file_upload_preferences() still filtered site_id = current, so it never found a shared directory.

The visible symptom on MSM sites:

1. Upload a file to a shared directory that fails a post-move check. Reproduce reliably by dropping a .webp into a shared directory that allows only Documents.
2. Filemanager::_upload_error() calls file_model::delete_raw_file(), which looks the directory up through the legacy model and gets an empty result.
3. PHP raises Undefined array key "server_path" (legacy/models/file_model.php:634). The HTML error output replaces the JSON response, so the drag-and-drop uploader shows the generic "Unexpected error. Check your post_max_size setting" message instead of the real error ("file type not allowed", "exceeds max dimensions", etc.).
4. The @unlink() calls run against a null path, so the file that should have been cleaned up stays in the directory. Users report that the upload "errored but uploaded anyway".

Non-MSM installs and non-shared directories are unaffected, which is why this is hard to reproduce locally.

Change

get_file_upload_preferences() now filters where_in('site_id', [0, current_site_id]) unless $ignore_site_id is passed, matching the modern models. This fixes delete_raw_file() and the other legacy callers that look up a shared directory by ID (Filemanager::fetch_files(), metaweblog, moblog). List callers now include shared directories, which matches the modern file pickers and fieldtypes. parse_upload_path_vars() already handles site_id 0 (no per-site overrides).

Tests

• New Tests/ExpressionEngine/legacy/Models/FileUploadPreferencesModelTest.php: an ID lookup includes site_id 0 and returns server_path; $ignore_site_id skips the site filter. It fails on 7.dev without the change.
• Addons/file (232), Service/File (11), Library/Filesystem (10), legacy/Helpers, legacy/Core, legacy/database, legacy/Api: same results before and after.
• Pre-existing failures on 7.dev, unchanged by this PR: GridModelOrderingTest::testOrdersByMultipleGridColumns ("Cannot call constructor") and CacheAdapterFallbackToFileTest::testDefaultsToFileAdapter (child process ended unexpectedly). Locally the full suite also stops at about 10% with "The configuration file does not exist.", so it was run by area.