refactor: migrate from Codeberg to Gitea and rename rhemawave to radiantwave

- Update all Codeberg URLs to gitea.radiantwavetech.com/RadiantWaveTech/
- Rename flake inputs: rhemawave → radiantwave, rhemawave-dev → radiantwave-dev
- Rename NixOS configs: rhemawavekiosk* → radiantwavekiosk*
- Update systemd services, data paths, and binary references
- Rename plymouth theme files
- Update CI workflow, documentation, and build scripts

iso-config.nix

@@ -6,10 +6,10 @@
 }:
 let
   targetSystem =
-    self.nixosConfigurations.rhemawavekiosk.config.system.build.toplevel;
+    self.nixosConfigurations.radiantwavekiosk.config.system.build.toplevel;
 
   diskoScript =
-    self.nixosConfigurations.rhemawavekiosk.config.system.build.diskoScript;
+    self.nixosConfigurations.radiantwavekiosk.config.system.build.diskoScript;
 in
 {
   nix.settings = {
@@ -104,7 +104,7 @@ script = ''
 
       ${diskoScript}
 
-      echo "Installing RhemaWave"
+      echo "Installing RadiantWave"
       echo "Closure Path: ${targetSystem}"
 
       nixos-install \