refactor: track import progress per film instead of per batch

Replace batch-level progress (processedBatches/totalBatches) with
film-level progress (processedFilms/totalFilms) for smoother UI updates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

migrations/Version20260401000002.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260401000002 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Add processed_films column to import table';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE import ADD processed_films INT NOT NULL DEFAULT 0');
+        $this->addSql('ALTER TABLE import DROP COLUMN total_batches');
+        $this->addSql('ALTER TABLE import DROP COLUMN processed_batches');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE import DROP COLUMN processed_films');
+        $this->addSql('ALTER TABLE import ADD total_batches INT NOT NULL DEFAULT 0');
+        $this->addSql('ALTER TABLE import ADD processed_batches INT NOT NULL DEFAULT 0');
+    }
+}