fix(migrations): add ALTER TABLE fallback for media_sort_date column

When the storage.files table already exists from a manual migration,
CREATE TABLE IF NOT EXISTS is skipped entirely, so the new
media_sort_date column is never added. Add an ALTER TABLE ADD COLUMN
IF NOT EXISTS immediately after the CREATE TABLE to handle both fresh
and pre-existing databases.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

migrations/20260307000000_initial_schema.sql

@@ -560,6 +560,10 @@ CREATE TABLE IF NOT EXISTS storage.files (
     media_sort_date TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP
 );
 
+-- Ensure media_sort_date exists on pre-existing tables (CREATE TABLE IF NOT EXISTS skips it)
+ALTER TABLE storage.files ADD COLUMN IF NOT EXISTS
+    media_sort_date TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP;
+
 -- A user cannot have two non-trashed files with the same name in the same folder
 CREATE UNIQUE INDEX IF NOT EXISTS idx_files_unique_name_in_folder
     ON storage.files(folder_id, name, user_id) WHERE NOT is_trashed AND folder_id IS NOT NULL;