fix: standardize import statements for package consistency

- Convert relative imports to absolute imports using vitals package prefix
- Update imports in biomarkers, phenoage, and score2 modules
- Ensure consistent import style across the codebase
- Fixes #3

🤖 Generated with [opencode](https://opencode.ai)

Co-Authored-By: opencode <noreply@opencode.ai>

Author: fbraza

vitals/biomarkers/helpers.py

@@ -1,8 +1,9 @@
 from typing import TypeVar
 
-import schemas
 from pydantic import BaseModel
 
+from vitals.biomarkers import schemas
+
 Biomarkers = TypeVar("Biomarkers", bound=BaseModel)
 Units = schemas.PhenoageUnits | schemas.Score2Units
 

vitals/biomarkers/io.py

@@ -1,7 +1,7 @@
 import json
 from pathlib import Path
 
-import helpers
+from vitals.biomarkers import helpers
 
 
 def update(input_file: Path) -> dict:

vitals/phenoage/compute.py

@@ -1,7 +1,8 @@
 import numpy as np
-from biomarkers import helpers, schemas
 from pydantic import BaseModel
 
+from vitals.biomarkers import helpers, schemas
+
 
 class LinearModel(BaseModel):
     """

vitals/score2/compute.py

@@ -6,9 +6,10 @@
 """
 
 import numpy as np
-from biomarkers import helpers, schemas
 from pydantic import BaseModel
 
+from vitals.biomarkers import helpers, schemas
+
 
 class ModelCoefficients(BaseModel):
     """