feat(top-tags): surface top tags and genres across relevant views

queries/functions/get_top_tags.sql

@@ -0,0 +1,37 @@
+CREATE OR REPLACE FUNCTION get_top_tag_groups()
+RETURNS JSON AS $$
+BEGIN
+  RETURN json_build_object(
+    'tags', (
+      SELECT json_agg(t) FROM (
+        SELECT tag, COUNT(*) AS usage_count
+        FROM optimized_tagged_content
+        WHERE type IN ('article', 'link')
+        GROUP BY tag
+        ORDER BY usage_count DESC
+        LIMIT 10
+      ) t
+    ),
+    'watching_genres', (
+      SELECT json_agg(t) FROM (
+        SELECT tag, COUNT(*) AS usage_count
+        FROM optimized_tagged_content
+        WHERE type IN ('tv', 'movies')
+        GROUP BY tag
+        ORDER BY usage_count DESC
+        LIMIT 10
+      ) t
+    ),
+    'books_genres', (
+      SELECT json_agg(t) FROM (
+        SELECT tag, COUNT(*) AS usage_count
+        FROM optimized_tagged_content
+        WHERE type = 'books'
+        GROUP BY tag
+        ORDER BY usage_count DESC
+        LIMIT 10
+      ) t
+    )
+  );
+END;
+$$ LANGUAGE plpgsql STABLE;