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>

packages/db/package.json

@@ -16,7 +16,7 @@
     }
   },
   "scripts": {
-    "build": "tsc",
+    "build": "tsc --project .",
     "generate": "drizzle-kit generate",
     "migrate": "drizzle-kit migrate",
     "seed": "tsx src/seed.ts",