Dockerfile: simplify - clone emdash source, build all packages, copy with -L flag

Changes:
- Build all packages (core, auth, blocks, admin) from source
- Copy packages with -L dereferencing symlinks so deps resolve properly
- Use emdash@0.9.0 from npm (source packages include their own deps)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -17,6 +17,9 @@ importers:
       '@emdash-cms/plugin-audit-log':
         specifier: ^0.1.1
         version: 0.1.2(emdash@0.8.0(c5fdb61f10733b2502e0080090fb96d5))
+      '@lingui/react':
+        specifier: ^5.9.4
+        version: 5.9.5(react@19.2.4)
       astro:
         specifier: ^6.0.1
         version: 6.2.1(@types/node@25.6.0)(rollup@4.60.2)(typescript@5.9.3)(yaml@2.8.4)
@@ -35,6 +38,9 @@ importers:
       react-dom:
         specifier: 19.2.4
         version: 19.2.4(react@19.2.4)
+      react-hotkeys-hook:
+        specifier: ^5.2.4
+        version: 5.3.0(react-dom@19.2.4(react@19.2.4))(react@19.2.4)
     devDependencies:
       '@astrojs/check':
         specifier: ^0.9.7