feat(05-04): implement attach File, Thumb, blob bucket, system_files migration

- Winter-exact thumb filename and 3x3 partition with lazy imaging resize
- gocloud.dev/blob fileblob/memblob; empty bucket_url fails boot
- lagoon.Migrate runs system_files before every plugin set

lagoon/attach/migrations.go

@@ -1,7 +1,49 @@
 package attach
 
-import "github.com/go-gormigrate/gormigrate/v2"
+import (
+	"github.com/go-gormigrate/gormigrate/v2"
+	"gorm.io/gorm"
+)
 
-// Migrations is the framework-owned system_files set. lagoon.Migrate
-// runs it before every plugin set (D-14).
-var Migrations = []*gormigrate.Migration{}
+// Migrations creates Winter's system_files table. Folded from
+// modules/system/database/migrations/2013_10_01_000002_Db_System_Files.php
+// and 2025_04_10_000031_Db_Add_System_Files_Metadata.php.
+var Migrations = []*gormigrate.Migration{
+	{
+		ID: "202609180001_create_system_files",
+		Migrate: func(tx *gorm.DB) error {
+			stmts := []string{
+				`CREATE TABLE system_files (
+	id SERIAL PRIMARY KEY,
+	disk_name TEXT NOT NULL,
+	file_name TEXT NOT NULL,
+	file_size INTEGER NOT NULL,
+	content_type TEXT NOT NULL,
+	title TEXT,
+	description TEXT,
+	field TEXT,
+	attachment_id TEXT,
+	attachment_type TEXT,
+	is_public BOOLEAN NOT NULL DEFAULT TRUE,
+	sort_order INTEGER,
+	metadata TEXT,
+	created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+)`,
+				`CREATE INDEX system_files_field_index ON system_files (field)`,
+				`CREATE INDEX system_files_attachment_id_index ON system_files (attachment_id)`,
+				`CREATE INDEX system_files_attachment_type_index ON system_files (attachment_type)`,
+				`CREATE INDEX system_files_attachment_lookup_index ON system_files (attachment_type, attachment_id, field)`,
+			}
+			for _, stmt := range stmts {
+				if err := tx.Exec(stmt).Error; err != nil {
+					return err
+				}
+			}
+			return nil
+		},
+		Rollback: func(tx *gorm.DB) error {
+			return tx.Exec("DROP TABLE IF EXISTS system_files").Error
+		},
+	},
+}