fix(docker): use pnpm --filter for all monorepo package builds

Use pnpm --filter consistently for all three package builds in the
Dockerfile instead of mixing filter and cd approaches. Also set
--project . explicitly on tsc invocations to ensure tsconfig resolution
from the package directory rather than workspace root.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

package.json

@@ -5,7 +5,7 @@
   "type": "module",
   "scripts": {
     "dev": "tsx watch src/index.ts",
-    "build": "tsc -p .",
+    "build": "tsc --project .",
     "start": "node dist/index.js",
     "lint": "eslint src --ext .ts",
     "typecheck": "tsc --noEmit",