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.

models/scenario.py

@@ -19,6 +19,7 @@ from sqlalchemy.sql import func
 from config.database import Base
 from services.currency import normalise_currency
 from .enums import ResourceType, ScenarioStatus, sql_enum
+from .profitability_snapshot import ScenarioProfitability
 
 if TYPE_CHECKING:  # pragma: no cover
     from .financial_input import FinancialInput
@@ -75,6 +76,13 @@ class Scenario(Base):
         cascade="all, delete-orphan",
         passive_deletes=True,
     )
+    profitability_snapshots: Mapped[List["ScenarioProfitability"]] = relationship(
+        "ScenarioProfitability",
+        back_populates="scenario",
+        cascade="all, delete-orphan",
+        order_by=lambda: ScenarioProfitability.calculated_at.desc(),
+        passive_deletes=True,
+    )
 
     @validates("currency")
     def _normalise_currency(self, key: str, value: str | None) -> str | None:
@@ -83,3 +91,11 @@ class Scenario(Base):
 
     def __repr__(self) -> str:  # pragma: no cover
         return f"Scenario(id={self.id!r}, name={self.name!r}, project_id={self.project_id!r})"
+
+    @property
+    def latest_profitability(self) -> "ScenarioProfitability | None":
+        """Return the most recent profitability snapshot for this scenario."""
+
+        if not self.profitability_snapshots:
+            return None
+        return self.profitability_snapshots[0]