Add Multi-Period-modeling and stochastic modeling to flixopt

[FBumann]

Description

This PR collects all changes for the v3.0.0 release.
The main changes are the addition of multi period and stochastic modeling support

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

  • Multi-dimension modeling (time/period/scenario) with weights; scenario controls; NetCDF/JSON export, FlowResults with per-flow access; improved effect sharing syntax; balanced storage and new final-state storage options; enhanced plotting styles.

• Breaking Changes

  • Many public API renames and signature changes (model/submodel, invest/on‑off, inputs/outputs lists); plotting parameter renamed to style; calculation modeling now returns the Calculation object.

• Documentation

  • Major rework: mathematical notation, modeling patterns, scenarios, recipes, and new examples (scenarios, two‑stage).

• Chores

  • Logging defaults adjusted; optional logger-name and console stream settings.