Migrate from npm to pnpm across entire project

• Update all GitHub workflow files to use pnpm instead of npm
• Replace npm commands with pnpm equivalents in devcontainer scripts
• Remove package-lock.json files and update to use pnpm-lock.yaml
• Consolidate node version references to use server/.nvmrc

.github/workflows/fix-format.yml

@@ -33,7 +33,7 @@ jobs:
         with:
           node-version-file: './server/.nvmrc'
           cache: 'npm'
-          cache-dependency-path: '**/package-lock.json'
+          cache-dependency-path: '**/pnpm-lock.yaml'
 
       - name: Fix formatting
         run: make install-all && make format-all