Refactor database initialization and remove Alembic migrations

- Removed legacy Alembic migration files and consolidated schema management into a new Pydantic-backed initializer (`scripts/init_db.py`).
- Updated `main.py` to ensure the new DB initializer runs on startup, maintaining idempotency.
- Adjusted session management in `config/database.py` to prevent DetachedInstanceError.
- Introduced new enums in `models/enums.py` for better organization and clarity.
- Refactored various models to utilize the new enums, improving code maintainability.
- Enhanced middleware to handle JSON validation more robustly, ensuring non-JSON requests do not trigger JSON errors.
- Added tests for middleware and enums to ensure expected behavior and consistency.
- Updated changelog to reflect significant changes and improvements.

models/scenario.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 from datetime import date, datetime
-from enum import Enum
 from typing import TYPE_CHECKING, List
 
 from sqlalchemy import (
@@ -13,13 +12,14 @@ from sqlalchemy import (
     Numeric,
     String,
     Text,
+    UniqueConstraint,
 )
 from sqlalchemy.orm import Mapped, mapped_column, relationship, validates
 from sqlalchemy.sql import func
 
 from config.database import Base
 from services.currency import normalise_currency
-from .metadata import ResourceType
+from .enums import ResourceType, ScenarioStatus
 
 if TYPE_CHECKING:  # pragma: no cover
     from .financial_input import FinancialInput
@@ -27,18 +27,14 @@ if TYPE_CHECKING:  # pragma: no cover
     from .simulation_parameter import SimulationParameter
 
 
-class ScenarioStatus(str, Enum):
-    """Lifecycle states for project scenarios."""
-
-    DRAFT = "draft"
-    ACTIVE = "active"
-    ARCHIVED = "archived"
-
-
 class Scenario(Base):
     """A specific configuration of assumptions for a project."""
 
     __tablename__ = "scenarios"
+    __table_args__ = (
+        UniqueConstraint("project_id", "name",
+                         name="uq_scenarios_project_name"),
+    )
 
     id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
     project_id: Mapped[int] = mapped_column(
@@ -47,7 +43,9 @@ class Scenario(Base):
     name: Mapped[str] = mapped_column(String(255), nullable=False)
     description: Mapped[str | None] = mapped_column(Text, nullable=True)
     status: Mapped[ScenarioStatus] = mapped_column(
-        SQLEnum(ScenarioStatus), nullable=False, default=ScenarioStatus.DRAFT
+        SQLEnum(ScenarioStatus, name="scenariostatus", create_type=False),
+        nullable=False,
+        default=ScenarioStatus.DRAFT,
     )
     start_date: Mapped[date | None] = mapped_column(Date, nullable=True)
     end_date: Mapped[date | None] = mapped_column(Date, nullable=True)
@@ -55,7 +53,7 @@ class Scenario(Base):
         Numeric(5, 2), nullable=True)
     currency: Mapped[str | None] = mapped_column(String(3), nullable=True)
     primary_resource: Mapped[ResourceType | None] = mapped_column(
-        SQLEnum(ResourceType), nullable=True
+        SQLEnum(ResourceType, name="resourcetype", create_type=False), nullable=True
     )
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now()