Feature/containers-and-reprs-for-better-element-organization

[FBumann]

Description

Add Containers for Elements and results for better inspection and access patterns

Type of Change

• Bug fix
• New feature
• Documentation update
• Code refactoring

Related Issues

Closes #(issue number)

Testing

• I have tested my changes
• Existing tests still pass

Checklist

• My code follows the project style
• I have updated documentation if needed
• I have added tests for new functionality (if applicable)

Summary by CodeRabbit

• New Features

  • Rich, compact string representations for elements, storage and results (connections, sizes, invest params) and human-friendly sizing/invest-parameter formatting.

• Refactor

  • Unified, dict-like element access with grouped container views and improved, consistent reprs; results now guard and report missing flow data and expose scenario/period indexes.

• Tests

  • Functional tests updated to use dict-like lookup.

• Documentation

  • Changelog and user guide updated; legacy all_elements access deprecated.