docs: Update GEMINI.md with summary of event settings page

Added a summary of the new event settings page to GEMINI.md, documenting the form-based UI, collapsible sections, view toggles, and Svelte 5 reactivity improvements.

GEMINI.md

@@ -121,3 +121,14 @@ The new Badge Search functionality was refactored to resolve several issues rela
     - The badge search data flow was refactored to pass full badge objects from the search component to the list component, simplifying the logic and resolving reactivity issues.
 - **Link Generation:**
     - Badge links were updated to use the string-based random IDs for both the event and the badge, ensuring consistency and avoiding the exposure of internal numeric IDs.
+
+### Event Settings Page (2025-11-18)
+
+A new event settings page was created at `/events/[event_id]/settings` to provide a user-friendly interface for managing event configurations.
+
+**Key features:**
+
+-   **Form-Based UI:** Instead of raw JSON editing, the page uses form-based components for editing event properties. This includes basic event fields (name, code, dates, etc.) and the JSON configuration fields (`cfg_json`, `mod_pres_mgmt_json`, `mod_badges_json`, `mod_abstracts_json`).
+-   **Collapsible Sections:** Each configuration section is wrapped in a `<details>` element, allowing them to be collapsed and expanded for better organization.
+-   **View Toggling:** For the JSON configuration fields, a toggle switch allows the user to switch between the form-based UI and a raw JSON editor (using CodeMirror), providing flexibility for both simple and advanced editing.
+-   **Svelte 5 Reactivity:** The components were built using Svelte 5's `bindable` props to ensure proper two-way data binding between the parent page and the child form components. This corrected an issue where changes in the child components were not being reflected in the parent's state.