refactor: extract escapeRegex and validateTagSlugs server utils

Deduplicate tag validation and regex escaping into shared auto-imported
utils. Add tag validation to wiki patch/batch-tag routes. Remove
duplicate tags field from event schema.

server/api/members/directory.get.js

@@ -42,8 +42,7 @@ export default defineEventHandler(async (event) => {
   }
 
   if (search) {
-    // Escape regex metacharacters to prevent ReDoS
-    const escaped = search.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+    const escaped = escapeRegex(search);
     andConditions.push({
       $or: [
         { name: { $regex: escaped, $options: "i" } },