feat: Add support for WebDAV, NextCloud, OneDrive, and Google Drive storage

- Update config_form.templ to include form fields for new storage types
- Modify db.go to support generating rclone configs for WebDAV, NextCloud, OneDrive, and Google Drive
- Add migration to include new cloud storage fields in transfer_configs table
- Update migrations.go to include new cloud storage migration

internal/db/migrations/migrations.go

@@ -6,10 +6,11 @@ import (
 )
 
 // InitMigrations initializes the migrations
-func InitMigrations() *gormigrate.Gormigrate {
+func InitMigrations(db *gorm.DB) *gormigrate.Gormigrate {
 	migrations := []*gormigrate.Migration{
 		// ... existing migrations
 		AddDeleteAfterTransferColumn(),
+		AddCloudStorageFields(),
 	}
 	
 	return gormigrate.New(db, gormigrate.DefaultOptions, migrations)