refactor: Simplify Docker configuration by using .env file and streamline user/group settings

This commit refactors the `docker-compose.yml` and `Dockerfile` to simplify the management of environment variables and user/group configurations. The following changes were made:

1. **Environment Variables via `.env` File:**
   - Added `env_file: .env` in the base service configuration within `docker-compose.yml`. This allows for centralized management of environment variables, making it easier to configure different environments without modifying Docker files directly.

2. **User/Group Configuration Simplification:**
   - Removed hardcoded user and group settings (`USE_UID`, `USE_GID`, `USE_USER`, `USE_GROUP`) from the `docker-compose.yml` file.
   - Updated the `Dockerfile` to use default values of `0` for `USE_UID` and `USE_GID`, and `root` for `USE_USER` and `USE_GROUP`. This aligns with common practices where root is often used in containerized environments unless specified otherwise.

3. **Conditional Dependency Handling:**
   - Introduced conditional logic to enable dependencies like Krita based on the value of `USE_KRITA`.
   - Simplified the environment variable assignments within the Dockerfile, ensuring that only necessary variables are set.

4. **Entrypoint Script Enhancements:**
   - Added a feature in the `entrypoint.sh` script to update custom nodes by pulling the latest changes from their respective repositories if `UPDATE_CUSTOM_NODES` is set to `true`.

These changes improve the maintainability and flexibility of the Docker setup, making it easier to adapt to different deployment scenarios.

docker-compose.yml

@@ -6,6 +6,7 @@ x-base_service: &base_service
       - &v2 ./output:/output
     stop_signal: SIGKILL
     tty: true
+    env_file: .env
     deploy:
       resources:
         reservations:
@@ -47,10 +48,6 @@ services:
     image: sd-comfy:7
     environment:
       - CLI_ARGS=
-      - USE_UID=0
-      - USE_GID=0
-      - USE_USER=root
-      - USE_GROUP=root
     env_file: .env