Timeline: Create fixtures for timeline elements

[yepzdk]

Description

Create test fixtures that include timeline data for testing and development purposes.

Fixtures should include

• Project with multiple timeline items:
  • Referenced hearings
  • Referenced public meetings
  • Referenced decisions
  • Referenced dialogues
• Timeline note paragraphs with various dates
• Items with and without images
• Mix of completed, current, and upcoming statuses (dates in past/present/future)

Related files

• Fixture files in project (location TBD)
• web/modules/custom/hoeringsportal_project/src/Helper/ProjectHelper.php

Parent issue

Part of #598