Refactor investor and fund schemas to support new check size range

- Removed deprecated `stage_focus` column from `InvestorTable` and `InvestorSchema`.
- Updated `FundTable` to change `fund_size` from VARCHAR to INTEGER and added `check_size_lower` and `check_size_upper` columns.
- Modified API routes to return investor-fund combinations as separate entries.
- Created new `InvestorFundData` schema for combined investor-fund responses.
- Implemented LLM parsing for check size range from estimated investment size.
- Updated database migration script to reflect schema changes and ensure data integrity.
- Removed obsolete verification and test scripts related to the old schema.

preprocessor/models.py

@@ -223,11 +223,15 @@ class FundTable(Base, TimestampMixin):
 
     # Fund details
     fund_name = Column(String, nullable=True)
-    fund_size = Column(String, nullable=True)  # Store as string to preserve currency
+    fund_size = Column(
+        Integer, nullable=True
+    )  # Store as integer for numerical filtering
     fund_size_source_url = Column(String, nullable=True)
-    estimated_investment_size = Column(
-        String, nullable=True
-    )  # e.g., "EUR 1,000 to 2,000"
+
+    # Check size range (parsed from estimated_investment_size by LLM)
+    check_size_lower = Column(Integer, nullable=True)
+    check_size_upper = Column(Integer, nullable=True)
+
     source_url = Column(String, nullable=True)
     source_provider = Column(String, nullable=True)  # e.g., "Perplexity"