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.

tests/test_models_enums.py

@@ -0,0 +1,22 @@
+from sqlalchemy import Enum as SQLEnum
+
+from models.enums import (
+    MiningOperationType,
+    ScenarioStatus,
+    FinancialCategory,
+    DistributionType,
+)
+
+
+def test_enum_members_and_sql_names():
+    # Verify enum members exist
+    assert MiningOperationType.OTHER.value == "other"
+    assert ScenarioStatus.DRAFT.value == "draft"
+    assert FinancialCategory.REVENUE.value == "revenue"
+    assert DistributionType.NORMAL.value == "normal"
+
+    # Verify SQLAlchemy SQLEnum name mapping is consistent
+    assert SQLEnum(MiningOperationType, name="miningoperationtype").name == "miningoperationtype"
+    assert SQLEnum(ScenarioStatus, name="scenariostatus").name == "scenariostatus"
+    assert SQLEnum(FinancialCategory, name="financialcategory").name == "financialcategory"
+    assert SQLEnum(DistributionType, name="distributiontype").name == "distributiontype"