feat(website): store previewed sequence ID in URL

[theosanderson]

resolves #2025

preview URL: http://previewurl.loculus.org

Summary

Stores the ID of the sequence currently previewed in a modal on the search page in the URL

1. Modified both the previewedSeqId and previewHalfScreen state
   to initialize from URL parameters
2. Created callback functions to update both local state and
   URL state
3. Added a useEffect hook to keep the local state in sync with
   URL parameters when they change
4. Used the same pattern as the page parameter:
   - For selected sequence: selectedSeq=ABC123 in URL
   - For half screen mode: halfScreen=true in URL
   - Parameters are completely removed from URL when not active

Now when users:

1. Select a sequence for preview, it will be stored in the URL
2. Change to half-screen view, that preference will be stored
   in the URL
3. Reload the page or share the URL, both the selected sequence
   and view mode will be preserved

Tests aren't working atm though the function does

PR Overview

This PR updates the search page functionality to store the previewed sequence ID and half-screen preference in the URL, enabling state persistence on reload or when sharing the URL.

• Initializes state from URL parameters for sequence and view mode
• Introduces callbacks to update both local state and URL query parameters
• Adds tests to verify the URL parameter integration for sequence selection and half-screen view

Reviewed Changes

File	Description
website/src/components/SearchPage/SearchFullUI.tsx	Refactored state initialization and updated functions to synchronize URL parameters
website/tests/pages/search/index.spec.ts	Added integration tests for updating and restoring URL parameters

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (1)

website/src/components/SearchPage/SearchFullUI.tsx:121

• [nitpick] The callback function 'setPreviewedSeqId' shares a similar naming to the inner state setter 'setPreviewedSeqIdInner', which could be confusing. Consider renaming the callback to 'updatePreviewedSeqId' for improved clarity.

const setPreviewedSeqId = useCallback(