feat: Add profitability calculation schemas and service functions

- Introduced Pydantic schemas for profitability calculations in `schemas/calculations.py`.
- Implemented service functions for profitability calculations in `services/calculations.py`.
- Added new exception class `ProfitabilityValidationError` for handling validation errors.
- Created repositories for managing project and scenario profitability snapshots.
- Developed a utility script for verifying authenticated routes.
- Added a new HTML template for the profitability calculator interface.
- Implemented a script to fix user ID sequence in the database.

services/__init__.py

@@ -1,10 +1,12 @@
 """Service layer utilities."""
 
 from .pricing import calculate_pricing, PricingInput, PricingMetadata, PricingResult
+from .calculations import calculate_profitability
 
 __all__ = [
     "calculate_pricing",
     "PricingInput",
     "PricingMetadata",
     "PricingResult",
+    "calculate_profitability",
 ]