Refactor code structure for improved readability and maintainability

preprocessor/models.py

@@ -139,9 +139,7 @@ class InvestorTable(Base, TimestampMixin):
     headquarters = Column(String, nullable=True)
 
     # AUM fields
-    aum = Column(
-        String, nullable=True
-    )  # Store as string to preserve currency (e.g., "EUR 850,000,000")
+    aum = Column(Integer, nullable=True)  # Store as integer for numerical filtering
     aum_as_of_date = Column(String, nullable=True)
     aum_source_url = Column(String, nullable=True)
 
@@ -317,7 +315,7 @@ class SectorTable(Base, TimestampMixin):
     )
 
     projects = relationship(
-        "ProjectTable", secondary=project_sector_association, back_populates="projects"
+        "ProjectTable", secondary=project_sector_association, back_populates="sector"
     )