feat: Adds hydronic system pressure calculator.

Sources/ViewController/HomePage.swift

@@ -61,6 +61,12 @@ struct HomePage: HTML, Sendable {
         svg: .droplets,
         route: .psychrometrics(.index)
       )
+      group(
+        label: "Hydronic System Pressure",
+        description: HydronicSystemPressure.description,
+        svg: .circleGauge,
+        route: .hydronicSystemPressure(.index)
+      )
     }
   }