Feat: Implement interconnected organ simulation

This commit refactors the organ simulation to enable dynamic interactions between organs, replacing the previous "faked" or hardcoded connections.

Key changes include:
- Major Refactoring: Changed the `Organ::update` method signature to `update(Patient& patient, double deltaTime_s)`, allowing organs to access the shared patient state and other organs. This was propagated to all organ classes.
- Blood Chemistry Model: Introduced a central `Blood` struct in the `Patient` model to track shared resources like oxygen, CO2, glucose, and toxins.
- Organ System Interconnections:
    - Lungs & Brain: Lungs now perform gas exchange affecting the blood. The brain consumes O2, produces CO2, and its GCS is affected by hypoxia/hypercapnia.
    - Liver-Gallbladder: Gallbladder now receives bile directly from the liver's production rate.
    - Digestive System: Stomach passes chyme to the intestines, which absorb glucose into the blood. The pancreas responds to blood glucose changes.
    - Renal System: Kidneys' GFR is now influenced by the heart's aortic pressure, and they produce urine that fills the bladder directly.
    - Cardiovascular & Neurological: The heart rate responds to hypoxia, and the brain uses live aortic pressure from the heart.
- Comprehensive Test Scenario: Updated the main example to include a 60-second simulation with a meal and a lung injury event to verify the new interconnected system.

This creates a more realistic and scalable physiological simulation framework where organ behaviors are emergent from their interactions.

src/Bladder.cpp

@@ -1,4 +1,5 @@
 #include "MedicalLib/Bladder.h"
+#include "MedicalLib/Patient.h"
 #include <random>
 #include <algorithm>
 #include <sstream>
@@ -11,14 +12,7 @@ Bladder::Bladder(int id)
       pressure_cmH2O(5.0),
       internalSphincterClosed(true) {}
 
-void Bladder::update(double deltaTime_s) {
-    // In a connected model, this would be called by the Kidneys.
-    // For now, simulate a constant fill rate from the kidneys.
-    const double urineInflow_ml_per_s = 0.02;
-    if (currentState != MicturitionState::VOIDING) {
-        addUrine(urineInflow_ml_per_s * deltaTime_s);
-    }
-
+void Bladder::update(Patient& patient, double deltaTime_s) {
     // Simple pressure model: pressure increases with volume
     pressure_cmH2O = (currentVolume_mL / capacity_mL) * 60.0;