[chore] Replace pnpm with npm package manager

- Remove pnpm-specific files (pnpm-lock.yaml, pnpm-workspace.yaml)
- Update package.json scripts to use npm instead of pnpm
- Add npm workspaces configuration
- Update all GitHub workflow files to use npm
- Update documentation to reference npm commands
- Generate package-lock.json for npm dependency management

docs/adr/0002-monorepo-conversion.md

@@ -19,14 +19,13 @@ For more information on Monorepos, check out [monorepo.tools](https://monorepo.t
 
 ## Decision
 
-- Swap out NPM for PNPM
 - Add a workspace for the PrimeVue fork
 - Move the frontend code into its own app workspace
 - Longer term: Extract and reorganize common infrastructure to take advantage of the new monorepo tooling
 
 ### Tools proposed
 
-[PNPM](https://pnpm.io/) and [PNPM workspaces](https://pnpm.io/workspaces)
+[npm workspaces](https://docs.npmjs.com/cli/v8/using-npm/workspaces)
 
 For monorepo management, I'd probably go with [Nx](https://nx.dev/), but I could be conviced otherwise.
 There's a [whole list here](https://monorepo.tools/#tools-review) if you're interested.

docs/extensions/development.md

@@ -105,7 +105,7 @@ The alternative would have been breaking all existing extensions or staying with
 
 Build the frontend for full functionality:
 ```bash
-pnpm build
+npm run build
 ```
 
 For faster iteration during development, use watch mode: