Improve Docker Setup and Gradio Config Options

[MrLemur]

This PR introduces the following changes:

Docker Enhancements:

• Adds a .dockerignore file to prevent unnecessary files (e.g., models) from being copied into Docker images.
• Updates the Dockerfile to a functional version by removing an unused volume.
• Removes Miniconda from the Docker image to reduce its size.

Gradio Features:

• Adds an entrypoint script to support custom Gradio configuration files.
• Updates the Gradio script to allow users to select which model to load.

Documentation Updates:

• Recommends using CUDA 12.4 for improved compatibility.
• Updates the Docker README to reflect new configuration options.

Dependency Management:

• Explicitly declares all dependencies to ensure scripts run reliably.

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The Docker images can be accessed here: https://hub.docker.com/r/mrlemur/instantmesh

Fixes #178
Fixes #175