feat: Implement initial capex calculation feature

- Added CapexComponentInput, CapexParameters, CapexCalculationRequest, CapexCalculationResult, and related schemas for capex calculations.
- Introduced calculate_initial_capex function to aggregate capex components and compute totals and timelines.
- Created ProjectCapexRepository and ScenarioCapexRepository for managing capex snapshots in the database.
- Developed capex.html template for capturing and displaying initial capex data.
- Registered common Jinja2 filters for formatting currency and percentages.
- Implemented unit and integration tests for capex calculation functionality.
- Updated unit of work to include new repositories for capex management.

models/scenario.py

@@ -20,6 +20,7 @@ from config.database import Base
 from services.currency import normalise_currency
 from .enums import ResourceType, ScenarioStatus, sql_enum
 from .profitability_snapshot import ScenarioProfitability
+from .capex_snapshot import ScenarioCapexSnapshot
 
 if TYPE_CHECKING:  # pragma: no cover
     from .financial_input import FinancialInput
@@ -83,6 +84,13 @@ class Scenario(Base):
         order_by=lambda: ScenarioProfitability.calculated_at.desc(),
         passive_deletes=True,
     )
+    capex_snapshots: Mapped[List["ScenarioCapexSnapshot"]] = relationship(
+        "ScenarioCapexSnapshot",
+        back_populates="scenario",
+        cascade="all, delete-orphan",
+        order_by=lambda: ScenarioCapexSnapshot.calculated_at.desc(),
+        passive_deletes=True,
+    )
 
     @validates("currency")
     def _normalise_currency(self, key: str, value: str | None) -> str | None:
@@ -99,3 +107,11 @@ class Scenario(Base):
         if not self.profitability_snapshots:
             return None
         return self.profitability_snapshots[0]
+
+    @property
+    def latest_capex(self) -> "ScenarioCapexSnapshot | None":
+        """Return the most recent capex snapshot for this scenario."""
+
+        if not self.capex_snapshots:
+            return None
+        return self.capex_snapshots[0]