build: fix nix support, update flake

flake.lock

@@ -3,35 +3,32 @@
     "beaker-src": {
       "flake": false,
       "locked": {
-        "lastModified": 1775244490,
-        "narHash": "sha256-4TJv7X6D0l4rEbTRKf47gU43L8G5uJgxxtsqMkVixQY=",
+        "lastModified": 1790704008,
+        "narHash": "sha256-Al/BE7uVRSmUGF/t1m0pWxF9jNgzdCVUrc5ZHkcPiQg=",
         "ref": "refs/heads/master",
-        "rev": "3fab89ecf8f4c664477a82add660d28db87357b4",
-        "revCount": 27,
+        "rev": "10be7f581fb828e74f064ea7ad4fb0534ee8540a",
+        "revCount": 46,
         "shallow": false,
         "type": "git",
-        "url": "https://git.bwaaa.monster/beaker"
+        "url": "https://git.bwaaa.space/beaker"
       },
       "original": {
         "shallow": false,
         "type": "git",
-        "url": "https://git.bwaaa.monster/beaker"
+        "url": "https://git.bwaaa.space/beaker"
       }
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1773734432,
-        "narHash": "sha256-IF5ppUWh6gHGHYDbtVUyhwy/i7D261P7fWD1bPefOsw=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "cda48547b432e8d3b18b4180ba07473762ec8558",
-        "type": "github"
+        "lastModified": 1791456040,
+        "narHash": "sha256-gRZ/s8WQJ2CsXdhcDVQH34qxuL0MuMCOs3aBiK1Prsw=",
+        "rev": "e7439b6b14ad3cc35d05608ebca9bce01a25f5f8",
+        "type": "tarball",
+        "url": "https://releases.nixos.org/nixos/unstable/nixos-26.11pre1087755.e7439b6b14ad/nixexprs.tar.zst?lastModified=1791456040&rev=e7439b6b14ad3cc35d05608ebca9bce01a25f5f8"
       },
       "original": {
-        "owner": "NixOS",
-        "ref": "nixos-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
+        "type": "tarball",
+        "url": "https://channels.nixos.org/nixos-unstable/nixexprs.tar.zst"
       }
     },
     "root": {