Switch from Evolution to GNOME Calendar module

- Enable `calendar.enable` instead of `evolution.enable` in all host
  system‑modules files.
- Add `modules/core/calendar.nix` defining the calendar option and
  installing GNOME Calendar and Contacts.
- Remove the deprecated `modules/core/evolution.nix` and update
  `core/default.nix` imports accordingly.
- Include the GNOME package set via `./gnome.nix` in
  `modules/core/packages/default.nix`.

hosts/Garand-Desktop/system-modules.nix

@@ -21,7 +21,7 @@ _: {
   /*
   Calendar & Contacts
   */
-  evolution.enable = true; # Evolution: calendar and contacts application
+  calendar.enable = true; # GNOME Calendar: calendar and contacts application
 
   /*
   Gaming
@@ -87,7 +87,7 @@ _: {
     Utilities / Misc
     */
     eddieAirVPN.enable = true; # Eddie AirVPN: VPN client
-    galculator.enable = false; # Galculator: simple calculator
+    gnomeCalculator.enable = true; # gnomeCalculator: simple calculator
     gedit.enable = true; # Gedit: GNOME text editor
     winboat.enable = true; # Winboat: Windows remote desktop via RDP
     adb.enable = false; # ADB: Android SDK platform tools

hosts/Garand-Laptop/system-modules.nix

@@ -21,7 +21,7 @@ _: {
   /*
   Calendar & Contacts
   */
-  evolution.enable = true; # Evolution: calendar and contacts application
+  calendar.enable = true; # GNOME Calendar: calendar and contacts application
 
   /*
   Gaming
@@ -87,7 +87,7 @@ _: {
     Utilities / Misc
     */
     eddieAirVPN.enable = true; # Eddie AirVPN: VPN client
-    galculator.enable = false; # Galculator: simple calculator
+    gnomeCalculator.enable = true; # gnomeCalculator: simple calculator
     gedit.enable = false; # Gedit: GNOME text editor
     winboat.enable = false; # Winboat: Windows remote desktop via RDP
     adb.enable = false; # ADB: Android SDK platform tools

hosts/default/system-modules.nix

@@ -21,7 +21,7 @@ _: {
   /*
   Calendar & Contacts
   */
-  evolution.enable = true; # Evolution: calendar and contacts application
+  calendar.enable = true; # GNOME Calendar: calendar and contacts application
 
   /*
   Gaming
@@ -87,7 +87,7 @@ _: {
     Utilities / Misc
     */
     eddieAirVPN.enable = true; # Eddie AirVPN: VPN client
-    galculator.enable = false; # Galculator: simple calculator
+    gnomeCalculator.enable = true; # gnomeCalculator: simple calculator
     gedit.enable = false; # Gedit: GNOME text editor
     winboat.enable = false; # Winboat: Windows remote desktop via RDP
     adb.enable = false; # ADB: Android SDK platform tools