Fix RTL: use fetchNodeModules instead of npm ci in buildPhase

npm ci in buildPhase hangs because the Nix build sandbox has no network
access. Adopt nix-bitcoin's approach: fetchNodeModules pre-fetches
node_modules as a fixed-output derivation (which has network access),
and the main build copies them offline. Uses the same node_modules hash
as upstream nix-bitcoin for RTL 0.15.8.

packages/rtl/default.nix

@@ -2,33 +2,37 @@
 , stdenvNoCC
 , nodejs_22
 , nodejs-slim_22
+, fetchNodeModules
 , fetchurl
 , makeWrapper
 }:
-
-let
+let self = stdenvNoCC.mkDerivation {
+  pname = "rtl";
   version = "0.15.8";
 
   src = fetchurl {
-    url = "https://github.com/Ride-The-Lightning/RTL/archive/refs/tags/v${version}.tar.gz";
+    url = "https://github.com/Ride-The-Lightning/RTL/archive/refs/tags/v${self.version}.tar.gz";
     hash = "sha256-8XdGyORxB2dkZRB/Yl7zh+Quqo4L/Y0VmC6Brbr/hqU=";
   };
 
-in stdenvNoCC.mkDerivation {
-  pname = "rtl";
-  inherit version src;
+  passthru = {
+    nodejs = nodejs_22;
+    nodejsRuntime = nodejs-slim_22;
+
+    nodeModules = fetchNodeModules {
+      inherit (self) src nodejs;
+      # TODO-EXTERNAL: Remove `npmFlags` when no longer required
+      # See: https://github.com/Ride-The-Lightning/RTL/issues/1182
+      npmFlags = "--legacy-peer-deps";
+      hash = "sha256-oMqd6nLzS6iQ9w4z2yzpR2unA5qhOq5YdvfoS8IgYLY=";
+    };
+  };
 
   nativeBuildInputs = [
     makeWrapper
-    nodejs_22
   ];
 
-  phases = "unpackPhase buildPhase installPhase";
-
-  buildPhase = ''
-    # Install dependencies using npm ci (requires package-lock.json)
-    npm ci --legacy-peer-deps --ignore-scripts
-  '';
+  phases = "unpackPhase patchPhase installPhase";
 
   # `src` already contains the precompiled frontend and backend.
   # Copy all files required for packaging, like in
@@ -41,25 +45,20 @@ in stdenvNoCC.mkDerivation {
       package.json \
       frontend \
       backend \
-      node_modules \
+      ${self.nodeModules}/lib/node_modules \
       $dest
 
-    makeWrapper ${nodejs-slim_22}/bin/node "$out/bin/rtl" \
+    makeWrapper ${self.nodejsRuntime}/bin/node "$out/bin/rtl" \
       --add-flags "$dest/rtl.js"
 
     runHook postInstall
   '';
 
-  passthru = {
-    nodejs = nodejs_22;
-    nodejsRuntime = nodejs-slim_22;
-  };
-
   meta = with lib; {
-    description = "A web interface for LND";
+    description = "A web interface for LND, c-lightning and Eclair";
     homepage = "https://github.com/Ride-The-Lightning/RTL";
     license = licenses.mit;
     maintainers = with maintainers; [ ];
     platforms = platforms.unix;
   };
-}
+}; in self