feat(constraints): Add PRIMARY KEY constraint support and enhance column management tests

- Add PRIMARY KEY to constraint types in features.json
- Update constraints API to handle PRIMARY KEY operations
- Add PRIMARY KEY to constraint listing query
- Add validation and tests for PRIMARY KEY constraints
- Add tests for DEFAULT value and NOT NULL in column management
- Update ROADMAP.md to mark PRIMARY KEY, DEFAULT, and NOT NULL as complete
- Update README.md with new constraint capabilities
- Update TESTING.md with comprehensive test coverage (105 total tests)

Co-authored-by: johndoe6345789 <224850594+johndoe6345789@users.noreply.github.com>

src/utils/featureConfig.test.ts

@@ -280,6 +280,15 @@ describe('FeatureConfig', () => {
       });
     });
 
+    it('should include PRIMARY KEY constraint type', () => {
+      const constraintTypes = getConstraintTypes();
+      const primaryKeyConstraint = constraintTypes.find(ct => ct.name === 'PRIMARY KEY');
+      
+      expect(primaryKeyConstraint).toBeDefined();
+      expect(primaryKeyConstraint?.requiresColumn).toBe(true);
+      expect(primaryKeyConstraint?.requiresExpression).toBe(false);
+    });
+
     it('should include UNIQUE constraint type', () => {
       const constraintTypes = getConstraintTypes();
       const uniqueConstraint = constraintTypes.find(ct => ct.name === 'UNIQUE');