feat: add versioned research templates and alpha variants

backend/app/research/contracts.py

@@ -1,6 +1,5 @@
 """Explicit snapshot and field-binding contracts for research producers."""
 
-import re
 from typing import Literal
 
 from pydantic import Field, model_validator
@@ -8,8 +7,7 @@ from pydantic import Field, model_validator
 from ..backtests.contracts import SimulationSettings, Source
 from ..catalog.contracts import Scope
 from ..schemas import Contract
-
-PLACEHOLDER = re.compile(r"\{([A-Za-z_][A-Za-z0-9_]*)\}")
+from .expressions import PLACEHOLDER
 
 
 class ResearchInputSelection(Contract):