docs: Update project documentation and session notes

- Updates `GEMINI.md` with a detailed summary of the days debugging session for the v3 Badges page.
- Updates `TODO.md` to mark recent bug fixes as complete and adds new tasks for outstanding issues (e.g., `order_by_li` fix).
- Updates `ARCHITECTURE.md` to reflect the current state of the tech stack (Tailwind v4, component library status).
- Creates `README.md` files for the new v3 Badges module and the legacy Lead Retrieval module to clarify their purpose and status.

GEMINI.md

@@ -148,3 +148,17 @@ To address issues with the Aether API's strict handling of `POST` and `PATCH` re
     - The `create_ae_obj__event` and `update_ae_obj__event` functions now use this whitelist to filter the `data_kv` object, ensuring only allowed fields are sent to the API. This provides a more maintainable and less error-prone way to manage which fields are sent to the API.
 - **Component Cleanup:** The temporary pre-cleaning logic from the `handle_save` function in `src/routes/events/[event_id]/settings/+page.svelte` has been removed, as the filtering is now handled centrally in `ae_events__event.ts`.
 - **Future Work:** This pattern of using a whitelist for editable fields will be applied to all other Aether object types to ensure consistent and correct API interactions across the application.
+
+### Badge Search v3 Bug-Fixing Session (2025-11-19)
+
+This session focused on resolving a series of cascading build and runtime errors that prevented the new "Badges v3" feature from loading and functioning correctly.
+
+- **Initial State:** The page was failing with a `Cannot use @variant with unknown variant: md` error, caused by a conflict between Skeleton UI's CSS and the project's Tailwind CSS v4 configuration.
+- **Misguided Fix & Reversal:** An initial attempt to fix this by removing all global Skeleton UI CSS imports from `app.css` resolved the `@variant` error but broke site-wide styling, causing errors like `Cannot apply unknown utility class 'preset-tonal-secondary'`. The Skeleton imports were subsequently restored to stabilize the application.
+- **Svelte v5 Event Syntax:** A significant amount of time was spent incorrectly attempting to "fix" Svelte v5 event handlers. The correct understanding was eventually established:
+    - **DOM Events:** Use the `onevent` prefix (e.g., `onclick`).
+    - **Component Events:** Continue to use the `on:event` directive (e.g., `on:success`).
+- **Invalid Attribute Name Error:** An error (`'onsubmit|preventDefault' is not a valid attribute name`) was discovered in the new badge forms. This was resolved by removing the `|preventDefault` modifier from the `onsubmit` attribute and instead calling `event.preventDefault()` inside the handler function. This appears to be a nuance or bug in how the Svelte v5 compiler handles modifiers with the new `on` prefix.
+- **Svelte 5 Binding Error:** A runtime error, `props_invalid_value: Cannot do bind:prop={undefined}`, was fixed. It was caused by binding a parent component's `undefined` store value to a child component's prop that had a fallback. The fix involved adding a defensive initialization check directly in the parent component's `<script>` block to ensure the store value was not `undefined` before rendering. Using `onMount` was attempted first but proved incorrect as it runs too late in the lifecycle.
+- **API Fetch Error:** The final blocker was a `TypeError: NetworkError` during badge searches. This was traced to the `order_by_li` parameter being sent to the API in a format that was causing the `fetch` request to be aborted by the browser (likely due to a CORS preflight failure). The immediate fix, identified by the user, was to comment out the `order_by_li` parameter in the `search__event_badge` function call within `src/lib/ae_events/ae_events__event_badge.ts`.
+- **Git Issues:** A strange issue was encountered where `git add` commands were not successfully staging files, leading to multiple failed commit attempts. This resolved itself without a clear cause.