fix: Add npm to Railway build configuration

Fixes Railway deployment error where npm command was not found.

Changes:
- Added npm-9_x to nixPkgs in phases.setup
- Added --legacy-peer-deps flag for npm ci compatibility
- Improved command formatting for clarity

This resolves the "npm: command not found" error that was causing
repeated deployment failures on Railway.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: GeneAI

nixpacks.toml

@@ -1,11 +1,17 @@
 [phases.setup]
-nixPkgs = ["nodejs_20"]
+nixPkgs = ["nodejs_20", "npm-9_x"]
 
 [phases.install]
-cmds = ["cd website && npm ci"]
+cmds = [
+  "cd website",
+  "npm ci --legacy-peer-deps"
+]
 
 [phases.build]
-cmds = ["cd website && npm run build"]
+cmds = [
+  "cd website",
+  "npm run build"
+]
 
 [start]
 cmd = "cd website && npm run start"