feat: establish root config and workspace foundation

- Create browser-ext placeholder package.json for workspace resolution
- Update root engines to node >=22 matching .nvmrc and web/package.json
- pnpm-workspace.yaml already configured with web and browser-ext
- All legacy directories (packages/, services/, server/) already removed

pnpm-lock.yaml

@@ -24,6 +24,8 @@ importers:
         specifier: ^4.1.5
         version: 4.1.7(@types/node@25.9.1)(@vitest/coverage-v8@4.1.7)(jsdom@29.1.1)(vite@7.3.3(@types/node@25.9.1)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.48.0))
 
+  browser-ext: {}
+
   web:
     dependencies:
       '@solidjs/meta':