fix(flake.nix): update lockfile & add nix-prefetch-git (#16162)

Updated flake.lock and flake.nix dependencies, including:
- Updated flake.lock
- Updated vendorHash for coder binary
- Ensured pnpm 9.x uses nodejs 20
- Reordered development shell packages alphabetically

Change-Id: I3e5e9c9d1136ea8d03084bd13fdd723bff1680d9
Signed-off-by: Thomas Kosiewski <tk@coder.com>

flake.lock

@@ -29,11 +29,11 @@
         "systems": "systems"
       },
       "locked": {
-        "lastModified": 1726560853,
-        "narHash": "sha256-X6rJYSESBVr3hBoH0WbKE5KvhPU5bloyZ2L4K60/fPQ=",
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "c1dfcf08411b08f6b8615f7d8971a2bfa81d5e8a",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
         "type": "github"
       },
       "original": {
@@ -44,11 +44,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1729880355,
-        "narHash": "sha256-RP+OQ6koQQLX5nw0NmcDrzvGL8HDLnyXt/jHhL1jwjM=",
+        "lastModified": 1736883708,
+        "narHash": "sha256-uQ+NQ0/xYU0N1CnXsa2zghgNaOPxWpMJXSUJJ9W7140=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "18536bf04cd71abd345f9579158841376fdd0c5a",
+        "rev": "eb62e6aa39ea67e0b8018ba8ea077efe65807dc8",
         "type": "github"
       },
       "original": {
@@ -84,15 +84,15 @@
         ]
       },
       "locked": {
-        "lastModified": 1706694632,
-        "narHash": "sha256-ytyTwNPiUR8aq74QlxFI+Wv3MyvXz5POO1xZxQIoi0c=",
-        "owner": "nzbr",
+        "lastModified": 1737026290,
+        "narHash": "sha256-mETihodsu08H5rGC/UfeyIdqkA9saFNF2w3AzEG218I=",
+        "owner": "ThomasK33",
         "repo": "pnpm2nix-nzbr",
-        "rev": "0366b7344171accc2522525710e52a8abbf03579",
+        "rev": "c1f0ceeb759af20c5c232a9414036fda29a28a53",
         "type": "github"
       },
       "original": {
-        "owner": "nzbr",
+        "owner": "ThomasK33",
         "repo": "pnpm2nix-nzbr",
         "type": "github"
       }