nix: update flake inputs and dev shell tool versions

Refresh flake.lock (nixpkgs 2026-03-08 -> 2026-04-09) and bump the
tool pins that live directly in flake.nix:

  * golangci-lint 2.9.0 -> 2.11.4
  * protoc-gen-grpc-gateway 2.27.7 -> 2.28.0 (keeps the dev-shell
    code-gen tool in sync with the grpc-gateway Go module)
  * protobuf-language-server pinned commit bumped to ab4c128

Also replace nodePackages.prettier with the top-level prettier
attribute. nodePackages was removed from nixpkgs in the update and
the dev shell would otherwise fail to evaluate with:

    error: nodePackages has been removed because it was unmaintainable
           within nixpkgs

`nix flake check --all-systems` and `nix build .#headscale` both
pass, and `golangci-lint 2.11.4` reports no new issues on the tree.

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1772956932,
-        "narHash": "sha256-M0yS4AafhKxPPmOHGqIV0iKxgNO8bHDWdl1kOwGBwRY=",
+        "lastModified": 1775701739,
+        "narHash": "sha256-2FWWY1rr/+pGUJK1npcVcsWNEblzmKs6VxD3VEvwJSs=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "608d0cadfed240589a7eea422407a547ad626a14",
+        "rev": "0f7663154ff2fec150f9dbf5f81ec2785dc1e0db",
         "type": "github"
       },
       "original": {

flake.nix

@@ -62,16 +62,16 @@
 
           protoc-gen-grpc-gateway = buildGo rec {
             pname = "grpc-gateway";
-            version = "2.27.7";
+            version = "2.28.0";
 
             src = pkgs.fetchFromGitHub {
               owner = "grpc-ecosystem";
               repo = "grpc-gateway";
               rev = "v${version}";
-              sha256 = "sha256-6R0EhNnOBEISJddjkbVTcBvUuU5U3r9Hu2UPfAZDep4=";
+              sha256 = "sha256-93omvHb+b+S0w4D+FGEEwYYDjgumJFDAruc1P4elfvA=";
             };
 
-            vendorHash = "sha256-SOAbRrzMf2rbKaG9PGSnPSLY/qZVgbHcNjOLmVonycY=";
+            vendorHash = "sha256-jVP5zfFPfHeAEApKNJzZwuZLA+DjKgkL7m2DFG72UNs=";
 
             nativeBuildInputs = [ pkgs.installShellFiles ];
 
@@ -80,13 +80,13 @@
 
           protobuf-language-server = buildGo rec {
             pname = "protobuf-language-server";
-            version = "1cf777d";
+            version = "ab4c128";
 
             src = pkgs.fetchFromGitHub {
               owner = "lasorda";
               repo = "protobuf-language-server";
-              rev = "1cf777de4d35a6e493a689e3ca1a6183ce3206b6";
-              sha256 = "sha256-9MkBQPxr/TDr/sNz/Sk7eoZwZwzdVbE5u6RugXXk5iY=";
+              rev = "ab4c128f00774d51bd6d1f4cfa735f4b7c8619e3";
+              sha256 = "sha256-yF6kG+qTRxVO/qp2V9HgTyFBeOm5RQzeqdZFrdidwxM=";
             };
 
             vendorHash = "sha256-4nTpKBe7ekJsfQf+P6edT/9Vp2SBYbKz1ITawD3bhkI=";
@@ -97,16 +97,16 @@
           # Build golangci-lint with Go 1.26 (upstream uses hardcoded Go version)
           golangci-lint = buildGo rec {
             pname = "golangci-lint";
-            version = "2.9.0";
+            version = "2.11.4";
 
             src = pkgs.fetchFromGitHub {
               owner = "golangci";
               repo = "golangci-lint";
               rev = "v${version}";
-              hash = "sha256-8LEtm1v0slKwdLBtS41OilKJLXytSxcI9fUlZbj5Gfw=";
+              hash = "sha256-B19aLvfNRY9TOYw/71f2vpNUuSIz8OI4dL0ijGezsas=";
             };
 
-            vendorHash = "sha256-w8JfF6n1ylrU652HEv/cYdsOdDZz9J2uRQDqxObyhkY=";
+            vendorHash = "sha256-xuoj4+U4tB5gpABKq4Dbp2cxnljxdYoBbO8A7DqPM5E=";
 
             subPackages = [ "cmd/golangci-lint" ];
 
@@ -166,7 +166,7 @@
             golangci-lint
             golangci-lint-langserver
             golines
-            nodePackages.prettier
+            prettier
             nixpkgs-fmt
             goreleaser
             nfpm