Fix/poetry install double zip

[ruhrohraggy]

Description

Fixes a bug where Lambda layers created with poetry_install, pip_requirements, or npm_requirements incorrectly included both the installed dependencies AND the original source files, even when using
patterns to exclude them.

Root Cause

The module was unconditionally executing a "zip" step for the source path after dependency managers had already zipped their installed packages. This caused both the dependencies and pattern-filtered
source files to be included in the final zip.

Changes

• Modified package.py line 886 to make the source path zip step conditional
• Added comment explaining the logic
• Updated examples/build-package/main.tf to demonstrate using patterns with poetry_install
• Now only zips source path when NOT using dependency managers (pip_requirements, poetry_install, or npm_requirements)
• Dependency managers handle their own zipping correctly

Testing

Created a test Lambda layer with:
• Source files: src/, test/, terraform/, Makefile
• Poetry dependencies: requests and its dependencies
• Patterns excluding all source files

Before fix: Zip contained both python dependencies AND source files
After fix: Zip contains ONLY python/ directory with dependencies

Verified with:

unzip -l builds/*.zip | awk '{print $4}' | cut -d'/' -f1 | sort -u```
# Output: python (only)


## Example Usage
The updated example in examples/build-package/main.tf demonstrates the fix:
```hcl
source_path = [
  {
    path           = "${path.module}/../fixtures/python-app-poetry"
    poetry_install = true
    patterns = [
      "!ignore_please.txt", # Exclude this file
      "!index.py",          # Exclude source code
      "pyproject.toml",     # Include poetry config
      "poetry.lock",        # Include lock file
      "poetry.toml"         # Include poetry settings
    ]
  }
]

Breaking Changes

None. This fix makes the module behave as users would expect when using patterns with dependency managers.

Related Issues

This addresses the issue where patterns were ineffective at excluding source files when poetry_install, pip_requirements, or npm_requirements were enabled.