scope field

The project goal concept is represented by the scope field in the data model although renamed in UI. The scope field is required in the ProjectCreate pydantic model as per design. The scope field is included in the ProjectResponse to ensure it is always present. The scope field replaces hardcoded text in backend/app/workers/catalog.py to generate more accurate file summaries. Word count validation constrains the scope field to have a hard minimum of 20 words. Project Creation Form uses the scope field renamed as "Project Goal" in the UI for project creation. ProjectCreate validation for scope validates that the scope field meets minimum word count requirements.