feat: move db gen out, emit json field

sqlc.yaml

@@ -1,10 +1,13 @@
 version: "2"
 sql:
   - engine: "postgresql"
-    queries: "internal/author/query.sql"
-    schema: "internal/author/schema.sql"
+    queries: "db/query.sql"
+    schema: "db/schema.sql"
     gen:
       go:
-        package: "gen"
-        out: "internal/author/gen"
+        package: "db"
+        out: "internal/db"
         sql_package: "pgx/v5"
+        emit_json_tags: true
+        emit_interface: true
+        emit_pointers_for_null_types: true