[WIP] Update README and code documentation for trip header vs. event timezone logic

[Copilot]

Documentation and Code Updates for Trip Header vs. Event Timezone Logic

Plan

• Review current implementation and understand the timezone logic requirements
• Update code comments in ParseICalFeed.cs to explain trip header vs. event timezone handling
• Update code comments in TripEvent.cs model to clarify timezone behavior
• Update README.md to document the timezone logic and its rationale
• Add usage examples showing the timezone behavior difference
• Build and validate changes

Understanding

The code already identifies trip header events using IsTripHeadEvent property (determined by checking if description starts with "{travelerName} is in"). Currently, all events convert times to UTC. The issue requests documentation to explain when and why different timezones are used for:

• Trip Header Events: Use Europe/Berlin timezone for proper calendar display
• Individual Trip Events: Use UTC for consistent processing

Original prompt

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This section details on the original issue you should resolve

<issue_title>Update README and code documentation for trip header vs. event timezone logic</issue_title>
<issue_description>Recent changes introduced logic to distinguish between iCal objects that are header trips (main trip containers) and those that are individual trip events. The header trip now needs to be created with the European timezone, while all other events should use UTC for proper calendar display.

Action items:

• Update the README to document this logic and clarify the difference between header trips and event components in the iCal parsing process.
• Add or revise code comments wherever this distinction is implemented in the codebase.
• Ensure both usage examples and code documentation clearly explain when and why to use different timezones for header trips and events.

The logic itself is minimal, but strong documentation is needed to help users understand the intended behavior.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #7

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