fix: use logger.exception() in calculate_pitcher_ratings error handler

Replaces logger.error() with logger.exception() so the full stack trace
is captured when a pitcher card fails to generate, making it possible to
diagnose the root cause rather than just seeing the error message.

Closes #17

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pitchers/creation.py

@@ -301,8 +301,10 @@ async def calculate_pitching_cards(
                     "batting": f"#1W{df_data['pitch_hand']}-C",
                 }
             )
-        except Exception as e:
-            logger.error(f"Skipping fg ID {df_data['key_fangraphs']} due to: {e}")
+        except Exception:
+            logger.exception(
+                f"Skipping fg ID {df_data['key_fangraphs']} due to exception"
+            )
 
     print("Calculating pitching cards...")
     pitching_stats.apply(create_pitching_card, axis=1)