fix: Resolve Ruff E402 warnings and clean up imports across multiple modules

services/financial.py

@@ -1,7 +1,7 @@
-from __future__ import annotations
-
 """Financial calculation helpers for project evaluation metrics."""
 
+from __future__ import annotations
+
 from dataclasses import dataclass
 from datetime import date, datetime
 from math import isclose, isfinite
@@ -151,7 +151,8 @@ def internal_rate_of_return(
 
     amounts = [amount for amount, _ in flows]
     if not any(amount < 0 for amount in amounts) or not any(amount > 0 for amount in amounts):
-        raise ValueError("cash_flows must include both negative and positive values")
+        raise ValueError(
+            "cash_flows must include both negative and positive values")
 
     def _npv_with_flows(rate: float) -> float:
         periodic_rate = rate / float(compounds_per_year)
@@ -170,7 +171,8 @@ def internal_rate_of_return(
         derivative = 0.0
         for amount, periods in flows:
             factor = (1.0 + periodic_rate) ** (-periods - 1.0)
-            derivative += -amount * periods * factor / float(compounds_per_year)
+            derivative += -amount * periods * \
+                factor / float(compounds_per_year)
         return derivative
 
     rate = float(guess)
@@ -199,7 +201,8 @@ def internal_rate_of_return(
         attempts += 1
 
     if lower_value * upper_value > 0:
-        raise ConvergenceError("IRR could not be bracketed within default bounds")
+        raise ConvergenceError(
+            "IRR could not be bracketed within default bounds")
 
     for _ in range(max_iterations * 2):
         midpoint = (lower_bound + upper_bound) / 2.0
@@ -245,4 +248,5 @@ def payback_period(
         cumulative = next_cumulative
         previous_period = periods
 
-    raise PaybackNotReachedError("Cumulative cash flow never becomes non-negative")
+    raise PaybackNotReachedError(
+        "Cumulative cash flow never becomes non-negative")