fix(railway): move .dockerignore to docker/ to unblock Nixpacks builds (#1336)

.dockerignore at repo root excludes scripts/, docs/, and e2e/ from the
build context. Nixpacks (and/or Railway's build system) respects this
file, causing all seed cron services to crash with "Cannot find module
'/app/scripts/...'" at runtime.

Moving .dockerignore into docker/ (alongside the Dockerfile) means:
- Railway Nixpacks builds get the full repo (scripts/ included)
- GHA Docker builds use context: . with file: docker/Dockerfile,
  and Docker only reads .dockerignore from the build context root,
  so docker/ placement is harmless for GHA

docker/.dockerignore

@@ -0,0 +1,23 @@
+node_modules
+npm-debug.log*
+yarn.lock
+.pnpm-store
+
+.git
+.gitignore
+.github
+
+dist
+coverage
+.DS_Store
+
+src-tauri
+e2e
+scripts
+docs
+.planning
+
+*.log
+Dockerfile
+.dockerignore
+