feat: Add Processing Opex functionality

- Introduced OpexValidationError for handling validation errors in processing opex calculations.
- Implemented ProjectProcessingOpexRepository and ScenarioProcessingOpexRepository for managing project and scenario-level processing opex snapshots.
- Enhanced UnitOfWork to include repositories for processing opex.
- Updated sidebar navigation and scenario detail templates to include links to the new Processing Opex Planner.
- Created a new template for the Processing Opex Planner with form handling for input components and parameters.
- Developed integration tests for processing opex calculations, covering HTML and JSON flows, including validation for currency mismatches and unsupported frequencies.
- Added unit tests for the calculation logic, ensuring correct handling of various scenarios and edge cases.

models/__init__.py

@@ -29,6 +29,10 @@ from .simulation_parameter import SimulationParameter
 from .user import Role, User, UserRole, password_context
 from .profitability_snapshot import ProjectProfitability, ScenarioProfitability
 from .capex_snapshot import ProjectCapexSnapshot, ScenarioCapexSnapshot
+from .processing_opex_snapshot import (
+    ProjectProcessingOpexSnapshot,
+    ScenarioProcessingOpexSnapshot,
+)
 
 __all__ = [
     "FinancialCategory",
@@ -37,12 +41,14 @@ __all__ = [
     "Project",
     "ProjectProfitability",
     "ProjectCapexSnapshot",
+    "ProjectProcessingOpexSnapshot",
     "PricingSettings",
     "PricingMetalSettings",
     "PricingImpuritySettings",
     "Scenario",
     "ScenarioProfitability",
     "ScenarioCapexSnapshot",
+    "ScenarioProcessingOpexSnapshot",
     "ScenarioStatus",
     "DistributionType",
     "SimulationParameter",