Implement page to vote and fix trigger

internal/migrations/sql/000001_init.up.sql

@@ -35,7 +35,7 @@ CREATE TRIGGER enforce_max_voters
         SELECT 1
         FROM elections e
         WHERE e.id = NEW.election_id
-          AND e.max_voters IS NOT NULL
+          AND e.max_voters != 0
     )
 BEGIN
     SELECT CASE