chore: update .gitignore and remove nix configuration files

- Add devenv and direnv to .gitignore for local development environment
- Remove default.nix and flake.nix in favor of devenv.nix setup
- Clean up development environment configuration

Author: GSMLG-BOT

.gitignore

@@ -30,3 +30,10 @@ caddyserver-*.tar
 /priv/data
 /priv/bin
 
+
+# devenv
+.devenv/
+.devenv.*
+
+# direnv
+.direnv