feat: enforce 32-character minimum for description field in uploads

feat: Make description field mandatory with 32-character minimum requirement

CHANGES:

1. Description Field Validation

   • Changed description from optional to mandatory field
   • Enforced minimum 32-character requirement
   • Added double-layer validation (CLI + API)

2. CLI User Experience Improvements

   • Added prompt loop until valid description provided
   • Shows character count feedback: "⚠️ Description too short (X/32 characters)"
   • Provides helpful suggestion for better descriptions
   • Clear error messages with requirements

3. API-Level Validation

   • Returns "Description is required for upload" if empty
   • Returns "Description must be at least 32 characters (currently X characters)" if too short
   • Prevents uploads without valid description metadata

4. Test Coverage

   • Updated all existing tests with 32+ character descriptions
   • Added test_finalize_upload_missing_description() - validates empty rejection
   • Added test_finalize_upload_short_description() - validates length requirement
   • All 36 tests passing

IMPACT:

• Users must provide meaningful descriptions (32+ chars) for uploads
• Better data quality with minimum description length
• Clear user guidance during upload process
• No uploads proceed without proper description

BREAKING CHANGES:

• Existing scripts must include descriptions with minimum 32 characters
• Uploads with shorter descriptions will fail with clear error messages

FILES MODIFIED:

• src/corpus_client_cli/upload.py (description validation logic)
• tests/test_async_logic.py (updated tests with new validation)
• After