fix: provide curl or another uv installation path in Dockerfile

## Problem

The default Docker build invokes `curl` in the exporter stage, but the configured base image (`python:3.11-slim-bookworm`) does not include `curl`.

This affects current `main` at `c6478aae9ab50a13fc54c0599a0a459396c15b99` and release `0.0.5`.

## Reproduction

On Docker Desktop 29.4.1 with a Linux amd64 daemon:

```console
docker build -t hi-pdf-parser-audit .
```

The build stops at Dockerfile line 5:

```text
/bin/sh: 1: curl: not found
process "/bin/sh -c curl -LsSf https://astral.sh/uv/install.sh | sh" did not complete successfully
```

## Expected behavior

The repository's default Dockerfile should build from its default `BASE_IMAGE` without requiring an undeclared executable.

## Impact

Users cannot build the documented/default container image, so the service deployment path is blocked before dependency installation.

## Why there is no PR in this report

The repair requires a maintainer choice about build dependencies and supply-chain policy: install and later remove `curl`, copy a pinned `uv` binary from a trusted image, or use another reviewed installation method. Each option changes the image/tooling dependency boundary, so this report does not select one without approval.

Start by reading the default Dockerfile around line 5 and reproduce the failure with `docker build -t hi-pdf-parser-audit .` using the default `BASE_IMAGE`. Confirm the maintainer-approved installation method and supply-chain policy, then verify that the default image builds successfully without the missing executable error.

Written by the indexing model from the issue text.