fix(asana): use float8 instead of double for PostgreSQL compatibility

The migration used gorm:"type:double" which is MySQL-specific.
PostgreSQL does not have a "double" type and fails with:
  ERROR: type "double" does not exist (SQLSTATE 42704)

Changed to float8 which works on both MySQL (alias for double) and
PostgreSQL (alias for double precision).

Closes #8835

Author: tengtian

backend/plugins/asana/models/migrationscripts/20250212_add_task_transformation_fields.go

@@ -32,7 +32,7 @@ type asanaTask20250212 struct {
 	StdType         string   `gorm:"type:varchar(255)"`
 	StdStatus       string   `gorm:"type:varchar(255)"`
 	Priority        string   `gorm:"type:varchar(255)"`
-	StoryPoint      *float64 `gorm:"type:double"`
+	StoryPoint      *float64 `gorm:"type:float8"`
 	Severity        string   `gorm:"type:varchar(255)"`
 	LeadTimeMinutes *uint    `gorm:"type:int unsigned"`
 }