nix: bump npmDepsHash for the new preact dependency

frontend/package-lock.json changed (preact added to dashboard + shared
in the earlier commits on this branch) but the fixed-output npm-deps
hash pinned in nix/checks.nix, nix/packages/frontend.nix, and
nix/packages/swarm-ui.nix (all three hash the one shared lockfile,
per checks.nix's own comment) wasn't updated to match — argus caught
it on review. Recomputed with nix run nixpkgs#prefetch-npm-deps.

nix/checks.nix

@@ -152,7 +152,7 @@ in
     # Same lockfile as `frontend`/`swarm-ui` above — recompute in
     # lockstep with those two whenever `frontend/package-lock.json`
     # changes (`prefetch-npm-deps frontend/package-lock.json`).
-    npmDepsHash = "sha256-LIwW5Nn9cSqJHCm1czPIVxQdP5OqWk7U/4kvkwaj2ts=";
+    npmDepsHash = "sha256-8mYI9b1nuQ8YNFkW/ezJwO5Qw6NJTDG+kspYozs/5cI=";
 
     buildPhase = ''
       runHook preBuild

nix/packages/frontend.nix

@@ -40,7 +40,7 @@ buildNpmPackage {
   # Update whenever the lockfile changes. Recompute locally with the
   # same command (`pkgs.prefetch-npm-deps`), or let the build fail
   # and copy the actual hash from the error message.
-  npmDepsHash = "sha256-LIwW5Nn9cSqJHCm1czPIVxQdP5OqWk7U/4kvkwaj2ts=";
+  npmDepsHash = "sha256-8mYI9b1nuQ8YNFkW/ezJwO5Qw6NJTDG+kspYozs/5cI=";
 
   # `npm run build` recurses into all workspaces (`--workspaces
   # --if-present`). The workspaces' build scripts each run their own

nix/packages/swarm-ui.nix

@@ -35,7 +35,7 @@ buildNpmPackage {
   # Recompute with `prefetch-npm-deps frontend/package-lock.json`
   # whenever the lockfile changes — same value as `./frontend.nix`'s
   # `npmDepsHash`, both hash the one shared lockfile.
-  npmDepsHash = "sha256-LIwW5Nn9cSqJHCm1czPIVxQdP5OqWk7U/4kvkwaj2ts=";
+  npmDepsHash = "sha256-8mYI9b1nuQ8YNFkW/ezJwO5Qw6NJTDG+kspYozs/5cI=";
 
   buildPhase = ''
     runHook preBuild