bump syncstorage-rs to unstable, remove nixos-25.05 pkgs

flake.lock

@@ -371,22 +371,6 @@
         "type": "github"
       }
     },
-    "nixpkgs_25-05": {
-      "locked": {
-        "lastModified": 1767313136,
-        "narHash": "sha256-16KkgfdYqjaeRGBaYsNrhPRRENs0qzkQVUooNHtoy2w=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "ac62194c3917d5f474c1a844b6fd6da2db95077d",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "nixos-25.05",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "pre-commit": {
       "inputs": {
         "flake-compat": "flake-compat_2",
@@ -420,7 +404,6 @@
         "lanzaboote": "lanzaboote",
         "nixos-hardware": "nixos-hardware",
         "nixpkgs": "nixpkgs",
-        "nixpkgs_25-05": "nixpkgs_25-05",
         "simple-nixos-mailserver": "simple-nixos-mailserver",
         "vscode-extensions": "vscode-extensions"
       }