flake.nix, flake.lock: bump nixpkgs and pinned tools

nixpkgs: bump unstable revision. Pinned tools: grpc-gateway 2.28.0 ->
2.29.0 (matches the Go dep), golangci-lint 2.11.4 -> 2.12.2. Disable
gomodguard in .golangci.yaml since 2.12 deprecated it.

.golangci.yaml

@@ -13,6 +13,7 @@ linters:
     - gochecknoinits
     - gocognit
     - godox
+    - gomodguard
     - interfacebloat
     - ireturn
     - lll

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1777270315,
-        "narHash": "sha256-yKB4G6cKsQsWN7M6rZGk6gkJPDNPIzT05y4qzRyCDlI=",
+        "lastModified": 1779351318,
+        "narHash": "sha256-f+JACbTqzZ+G92DSnXOUGRhGANb8Blh7CoeYOeBF8/U=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "6368eda62c9775c38ef7f714b2555a741c20c72d",
+        "rev": "4a29d733e8a7d5b824c3d8c958a946a9867b3eb2",
         "type": "github"
       },
       "original": {

flake.nix

@@ -62,16 +62,16 @@
 
           protoc-gen-grpc-gateway = buildGo rec {
             pname = "grpc-gateway";
-            version = "2.28.0";
+            version = "2.29.0";
 
             src = pkgs.fetchFromGitHub {
               owner = "grpc-ecosystem";
               repo = "grpc-gateway";
               rev = "v${version}";
-              sha256 = "sha256-93omvHb+b+S0w4D+FGEEwYYDjgumJFDAruc1P4elfvA=";
+              sha256 = "sha256-d9OIIGttyMBSNgpS6mbR5JEIm13qGu2gFHJazJAexdw=";
             };
 
-            vendorHash = "sha256-jVP5zfFPfHeAEApKNJzZwuZLA+DjKgkL7m2DFG72UNs=";
+            vendorHash = "sha256-p51yD+v8+rPs+ztlX7r0VQ4XlwUkxu+PxgknKEvH00k=";
 
             nativeBuildInputs = [ pkgs.installShellFiles ];
 
@@ -97,16 +97,16 @@
           # Build golangci-lint with Go 1.26 (upstream uses hardcoded Go version)
           golangci-lint = buildGo rec {
             pname = "golangci-lint";
-            version = "2.11.4";
+            version = "2.12.2";
 
             src = pkgs.fetchFromGitHub {
               owner = "golangci";
               repo = "golangci-lint";
               rev = "v${version}";
-              hash = "sha256-B19aLvfNRY9TOYw/71f2vpNUuSIz8OI4dL0ijGezsas=";
+              hash = "sha256-qR7fp1x2S+EwEAcplRHTvA3jWwLr/XSiYKSZtAwkrNU=";
             };
 
-            vendorHash = "sha256-xuoj4+U4tB5gpABKq4Dbp2cxnljxdYoBbO8A7DqPM5E=";
+            vendorHash = "sha256-AG5wtLwWLz55bdp1oi3cW+9O3yj1W1P7MV9zxym7Pb4=";
 
             subPackages = [ "cmd/golangci-lint" ];