refactor(nvm): Move wrapper scripts to image_support_files directory

Improved code organization and maintainability:
- Created image_support_files/ directory for Docker helper scripts
- Moved bash-with-nvm and docker-entrypoint.sh to support directory
- Added comprehensive README.md documenting each script's purpose
- Updated Dockerfile to COPY from organized directory structure

Benefits:
- Cleaner repository structure
- Scripts are now version-controlled files (not echo chains)
- Easier to read, modify, and maintain
- Self-documented with in-directory README

No functional changes - all nvm functionality remains identical.

image_support_files/README.md

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+# Image Support Files
+
+This directory contains helper scripts that are copied into the Docker image during build to enable NVM functionality.
+
+## Files
+
+### `bash-with-nvm`
+
+**Purpose**: Wrapper script for Dockerfile RUN commands
+
+**Usage**: Set as SHELL directive in Dockerfile
+```dockerfile
+SHELL ["/usr/local/bin/bash-with-nvm"]
+```
+
+**What it does**:
+- Sources nvm before executing each Dockerfile RUN command
+- Enables direct usage of `nvm` commands without manual sourcing
+- Example: `RUN nvm install 18` works without `bash -c "source ..."`
+
+**Location in image**: `/usr/local/bin/bash-with-nvm`
+
+**How it works**:
+1. Exports NVM_DIR environment variable
+2. Sources `$NVM_DIR/nvm.sh` to load nvm functions
+3. Executes the command passed to it via `eval "$@"`
+
+---
+
+### `docker-entrypoint.sh`
+
+**Purpose**: ENTRYPOINT script for runtime nvm support
+
+**Usage**: Set as ENTRYPOINT in Dockerfile
+```dockerfile
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]
+```
+
+**What it does**:
+- Makes nvm available in `docker run ... bash -c` commands
+- Enables nvm in CI/CD workflow scripts
+- Passes through non-bash commands unchanged
+
+**Location in image**: `/usr/local/bin/docker-entrypoint.sh`
+
+**How it works**:
+1. Loads nvm in the entrypoint environment
+2. Detects if command is `bash -c ...`
+3. If yes: Injects `source /etc/bash.bashrc` before the user's command
+4. If no: Executes command as-is with `exec "$@"`
+
+**Examples**:
+- `docker run image bash -c "nvm install 18"` → nvm is available
+- `docker run image node --version` → Passes through to node binary
+- CI/CD: `run: nvm install 19` → Works automatically
+
+---
+
+## Why These Scripts Are Needed
+
+**The Problem**:
+- nvm is a bash function, not a binary executable
+- It must be sourced into each shell session
+- Docker RUN commands and `bash -c` don't automatically source it
+
+**The Solution**:
+1. **bash-with-nvm**: Makes Dockerfile RUN commands work
+2. **docker-entrypoint.sh**: Makes runtime `bash -c` commands work
+3. **/etc/bash.bashrc** (configured in Dockerfile): Makes interactive shells work
+
+Together, these provide seamless nvm access in all contexts.
+
+---
+
+## Maintenance
+
+**Modifying the scripts**:
+1. Edit the file in this directory
+2. Rebuild the Docker image
+3. Test with both `docker build` and `docker run` scenarios
+
+**Testing checklist**:
+- [ ] `RUN nvm install 18` works in Dockerfile
+- [ ] `docker run image bash -c "nvm install 18"` works
+- [ ] `docker run image node --version` still works (fallback)
+- [ ] CI/CD workflows can use nvm commands
+
+**Debugging**:
+- View script in running container: `docker run image cat /usr/local/bin/bash-with-nvm`
+- Test entrypoint manually: `docker run --entrypoint /bin/bash image -c "nvm --version"`

image_support_files/bash-with-nvm

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+#!/bin/bash
+set -e
+
+# Load nvm before executing Dockerfile RUN commands
+export NVM_DIR="/usr/local/nvm"
+[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
+
+# Execute the command passed to this wrapper
+eval "$@"

image_support_files/docker-entrypoint.sh

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+#!/bin/bash
+set -e
+
+# Load nvm in the entrypoint environment
+export NVM_DIR="/usr/local/nvm"
+[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
+
+# If command is bash -c, inject bashrc sourcing to make nvm available
+if [ "$1" = "bash" ] && [ "$2" = "-c" ]; then
+  shift 2
+  exec bash -c "source /etc/bash.bashrc && $*"
+else
+  exec "$@"
+fi