Upgrade Nix flake and deps (#439)

* Automated commit

* Fix link

---------

Co-authored-by: patrick-conscriptus[bot] <175414948+patrick-conscriptus[bot]@users.noreply.github.com>
Co-authored-by: Smaug123 <3138005+Smaug123@users.noreply.github.com>

CONTRIBUTING.md

@@ -44,7 +44,7 @@ git config blame.ignoreRevsFile .git-blame-ignore-revs
 ## Dependencies
 
 I try to keep this repository's dependencies as few as possible, because (for example) any consumer of the source generator will also consume this project via the attributes.
-When adding dependencies, you will need to `nix run .#fetchDeps` to obtain a new copy of [the dependency lockfile](./nix/deps.nix).
+When adding dependencies, you will need to `nix run .#fetchDeps` to obtain a new copy of [the dependency lockfile](./nix/deps.json).
 
 ## Branch strategy
 

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1760103332,
-        "narHash": "sha256-BMsGVfKl4Q80Pr9T1AkCRljO1bpwCmY8rTBVj8XGuhA=",
+        "lastModified": 1760596604,
+        "narHash": "sha256-J/i5K6AAz/y5dBePHQOuzC7MbhyTOKsd/GLezSbEFiM=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "870493f9a8cb0b074ae5b411b2f232015db19a65",
+        "rev": "3cbe716e2346710d6e1f7c559363d14e11c32a43",
         "type": "github"
       },
       "original": {