Fix category filter bug and add tab accessibility

The category tabs were not filtering because the generic tab event handler
was overwriting currentFilter with undefined (category tabs use data-category
not data-filter). Fixed by targeting only [data-filter] tabs and clearing
categoryFilter when switching to non-category tabs.

Added proper ARIA attributes for screen reader accessibility:
- role="tablist" on nav-tabs container
- role="tab" and aria-selected on all tab buttons
- Dynamic aria-selected updates on tab clicks

Also includes API support for category field and deploy script update.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

deploy

@@ -6,7 +6,7 @@ DIR=/var/www/my_webapp__2/www
 # Deploy code files
 rsync -avz --no-t --no-p --delete \
     --exclude 'data/' \
-    index.html api.php containers.json og-image.png ${HOST}:${DIR}
+    index.html api.php containers.json categories.json og-image.png ${HOST}:${DIR}
 
 # Deploy data directory protection
 scp data/index.php ${HOST}:${DIR}/data/index.php 2>/dev/null || true