Improving Docker Image Creation

Currently the Docker image for DB Sync is large, complex, and discourages customization. Given the majority of our users are using the docker image, I would like to revisit this strategy.

## Introduction

Docker images are built from the NixOS module. While this approach does have benefits in reproduceability, it also presents several challenges:

* **Image Size**: Recent releases are 1GB+, even though the binary is less that 100MB
* **Nix specific**: Store paths confuse non-Nix users
* **Bundled Configs**: Included network configuration makes customization difficult

The NixOS module has significant complexity, mostly bash wrappers that inject network-specific configuration from the [Cardano Operations Book](https://book.play.dev.cardano.org/).

A while back, we added [configuration options](https://github.com/IntersectMBO/cardano-db-sync/blob/master/doc/configuration.md) to tune DB Sync to each user's specific needs. While convenient, the batteries-included approach make customization more difficult.

## Proposed Solution

Instead of building the Docker images with Nix, I propose we take a hybrid approach:

1. Build static binaries with Nix
2. Use a simple Dockerfile to copy artifacts to the Docker image

### Example Workflow

```
# Create a static executable
nix build .#cardano-db-sync-linux

# Copy the executable to docker context
cp -L result/bin/cardano-db-sync docker/

# Build the docker image
docker build docker
```

### Configuration Files
The configuration files would **not** be available in the image. Instead, users have two options:

* **Option 1**: Mount the configs in a data volume
* **Option 2**: Create a derived image with the configs baked in

The latest configuration files are available in the [Cardano Operations Book](https://book.play.dev.cardano.org/), which matches the workflow for non-containerized installations.

### Benefits

* **10x smaller images**: 100MB instead of 1GB
* **Standard Docker Experience**: Easier for non-nix users to debug
* **Explicit Configuration**: Straightforward customization for all users