cli: default template url should come from the package itself rather than our gitea

This allow easier testing and also forks.

templates/flake.nix

@@ -0,0 +1,16 @@
+{
+  outputs =
+    { ... }:
+    {
+      templates = {
+        default = {
+          description = "Initialize a new clan flake";
+          path = ./new-clan;
+        };
+        minimal = {
+          description = "for clans managed via (G)UI";
+          path = ./minimal;
+        };
+      };
+    };
+}